diff --git a/src/db/db/dbNetlistCompare.cc b/src/db/db/dbNetlistCompare.cc
index 237fa1059..4ac53a39a 100644
--- a/src/db/db/dbNetlistCompare.cc
+++ b/src/db/db/dbNetlistCompare.cc
@@ -27,20 +27,49 @@
 #include "tlTimer.h"
 #include "tlEquivalenceClusters.h"
 #include "tlLog.h"
+#include "tlEnv.h"
 
 #include <cstring>
 
-//  verbose debug output
-//  TODO: make this a feature?
-// #define PRINT_DEBUG_NETCOMPARE
+namespace {
 
-//  verbose net graph output
-//  TODO: make this a feature?
-// #define PRINT_DEBUG_NETGRAPH
+struct GlobalCompareOptions
+{
+  GlobalCompareOptions ()
+  {
+    m_is_initialized = false;
+  }
 
-//  Add this define for case insensitive compare
-//  (applies to circuits, device classes)
-#define COMPARE_CASE_INSENSITIVE
+  void ensure_initialized ()
+  {
+    if (! m_is_initialized) {
+      //  $KLAYOUT_NETLIST_COMPARE_DEBUG_NETCOMPARE
+      debug_netcompare = tl::app_flag ("netlist-compare-debug-netcompare");
+      //  $KLAYOUT_NETLIST_COMPARE_DEBUG_NETGRAPH
+      debug_netgraph = tl::app_flag ("netlist-compare-debug-netgraph");
+      //  $KLAYOUT_NETLIST_COMPARE_CASE_SENSITIVE
+      compare_case_sensitive = tl::app_flag ("netlist-compare-case-sensitive");
+      m_is_initialized = true;
+    }
+  }
+
+  bool debug_netcompare;
+  bool debug_netgraph;
+  bool compare_case_sensitive;
+
+private:
+  bool m_is_initialized;
+};
+
+}
+
+static GlobalCompareOptions *options ()
+{
+  //  TODO: thread safe?
+  static GlobalCompareOptions s_options;
+  s_options.ensure_initialized ();
+  return &s_options;
+}
 
 //  A constant indicating a failed match
 const size_t failed_match = std::numeric_limits<size_t>::max ();
@@ -63,28 +92,25 @@ namespace db
 static int name_compare (const std::string &n1, const std::string &n2)
 {
   //  TODO: unicode support?
-#if defined(COMPARE_CASE_INSENSITIVE)
+  if (options ()->compare_case_sensitive) {
+    return strcmp (n1.c_str (), n2.c_str ());
+  } else {
 #if defined(_WIN32)
-  return _stricmp (n1.c_str (), n2.c_str ());
+    return _stricmp (n1.c_str (), n2.c_str ());
 #else
-  return strcasecmp (n1.c_str (), n2.c_str ());
-#endif
-#else
-  return strcmp (n1.c_str (), n2.c_str ());
+    return strcasecmp (n1.c_str (), n2.c_str ());
 #endif
+  }
 }
 
-#if defined(COMPARE_CASE_INSENSITIVE)
-static std::string normalize_name (const std::string &n)
+static inline std::string normalize_name (const std::string &n)
 {
-  return tl::to_upper_case (n);
+  if (options ()->compare_case_sensitive) {
+    return n;
+  } else {
+    return tl::to_upper_case (n);
+  }
 }
-#else
-static inline const std::string &normalize_name (const std::string &n)
-{
-  return n;
-}
-#endif
 
 // --------------------------------------------------------------------------------------------------------------------
 //  DeviceCompare definition and implementation
@@ -1515,11 +1541,12 @@ NetGraph::build (const db::Circuit *c, DeviceCategorizer &device_categorizer, Ci
   for (std::vector<NetGraphNode>::iterator i = m_nodes.begin (); i != m_nodes.end (); ++i) {
     i->apply_net_index (m_net_index);
   }
-#if defined(PRINT_DEBUG_NETGRAPH)
-  for (std::vector<NetGraphNode>::iterator i = m_nodes.begin (); i != m_nodes.end (); ++i) {
-    tl::info << i->to_string () << tl::noendl;
+
+  if (options ()->debug_netgraph) {
+    for (std::vector<NetGraphNode>::iterator i = m_nodes.begin (); i != m_nodes.end (); ++i) {
+      tl::info << i->to_string () << tl::noendl;
+    }
   }
-#endif
 
   //  create subcircuit virtual nodes
 
@@ -1543,11 +1570,12 @@ NetGraph::build (const db::Circuit *c, DeviceCategorizer &device_categorizer, Ci
   for (std::map<const db::SubCircuit *, NetGraphNode>::iterator i = m_virtual_nodes.begin (); i != m_virtual_nodes.end (); ++i) {
     i->second.apply_net_index (m_net_index);
   }
-#if defined(PRINT_DEBUG_NETGRAPH)
-  for (std::map<const db::SubCircuit *, NetGraphNode>::iterator i = m_virtual_nodes.begin (); i != m_virtual_nodes.end (); ++i) {
-    tl::info << i->second.to_string () << tl::noendl;
+
+  if (options ()->debug_netgraph) {
+    for (std::map<const db::SubCircuit *, NetGraphNode>::iterator i = m_virtual_nodes.begin (); i != m_virtual_nodes.end (); ++i) {
+      tl::info << i->second.to_string () << tl::noendl;
+    }
   }
-#endif
 }
 
 size_t
@@ -1560,34 +1588,48 @@ NetGraph::derive_node_identities_for_edges (NetGraphNode::edge_iterator e, NetGr
 
   std::vector<const NetGraphNode *> other_nodes;
   other_nodes.reserve (ee - e);
-#if defined(PRINT_DEBUG_NETCOMPARE)
-  tl::info << indent(depth) << "consider transitions:";
-#endif
+  if (options ()->debug_netcompare) {
+    tl::info << indent(depth) << "considering transitions:";
+  }
+
+  bool first = true;
 
   for (NetGraphNode::edge_iterator i = e; i != ee; ++i) {
     if (i->second.first != net_index) {
       const NetGraphNode *nn = &node (i->second.first);
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << indent(depth) << "here: " << (nn->net() ? nn->net()->expanded_name().c_str() : "(null)") << " via";
-      for (std::vector<NetGraphNode::Transition>::const_iterator t = i->first.begin (); t != i->first.end(); ++t) {
-        tl::info << indent(depth) << "  " << t->to_string();
+      if (options ()->debug_netcompare) {
+        if (first) {
+          tl::info << indent (depth) << "  here: " << (node (net_index).net () ? node (net_index).net ()->expanded_name ().c_str () : "(null)") << " ->";
+          first = false;
+        }
+        tl::info << indent (depth) << "    " << (nn->net () ? nn->net ()->expanded_name ().c_str() : "(null)") << " via: " << tl::noendl;
+        for (std::vector<NetGraphNode::Transition>::const_iterator t = i->first.begin (); t != i->first.end(); ++t) {
+          tl::info << (t != i->first.begin () ? "; " : "") << t->to_string() << tl::noendl;
+        }
+        tl::info << "";
       }
-#endif
       nodes.push_back (nn);
     }
   }
 
   if (! nodes.empty ()) {   //  if non-ambiguous, non-assigned
 
+    first = true;
+
     for (NetGraphNode::edge_iterator i = e_other; i != ee_other; ++i) {
       if (i->second.first != other_net_index) {
         const NetGraphNode *nn = &data->other->node (i->second.first);
-#if defined(PRINT_DEBUG_NETCOMPARE)
-        tl::info << indent(depth) << "there: " << (nn->net() ? nn->net()->expanded_name().c_str() : "(null)") << " via";
-        for (std::vector<NetGraphNode::Transition>::const_iterator t = i->first.begin (); t != i->first.end(); ++t) {
-          tl::info << indent(depth) << "  " << t->to_string();
+        if (options ()->debug_netcompare) {
+          if (first) {
+            tl::info << indent (depth) << "  there: " << (data->other->node (other_net_index).net () ? data->other->node (other_net_index).net ()->expanded_name ().c_str () : "(null)") << " ->";
+            first = false;
+          }
+          tl::info << indent(depth) << "    " << (nn->net() ? nn->net()->expanded_name().c_str() : "(null)") << " via: " << tl::noendl;
+          for (std::vector<NetGraphNode::Transition>::const_iterator t = i->first.begin (); t != i->first.end(); ++t) {
+            tl::info << (t != i->first.begin () ? "; " : "") << t->to_string() << tl::noendl;
+          }
+          tl::info << "";
         }
-#endif
         other_nodes.push_back (nn);
       }
     }
@@ -1604,9 +1646,9 @@ NetGraph::derive_node_identities_for_edges (NetGraphNode::edge_iterator e, NetGr
     if (tentative) {
 
       if (nodes.size () != other_nodes.size ()) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-        tl::info << indent(depth) << "! rejected branch.";
-#endif
+        if (options ()->debug_netcompare) {
+          tl::info << indent(depth) << "=> rejected branch.";
+        }
         return failed_match;
       }
 
@@ -1614,9 +1656,9 @@ NetGraph::derive_node_identities_for_edges (NetGraphNode::edge_iterator e, NetGr
       if (nodes.size () > 1 || other_nodes.size () > 1) {
         for (size_t i = 0; i < nodes.size (); ++i) {
           if (! (*nodes[i] == *other_nodes[i])) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-            tl::info << indent(depth) << "! rejected branch.";
-#endif
+            if (options ()->debug_netcompare) {
+              tl::info << indent(depth) << "=> rejected branch.";
+            }
             return failed_match;
           }
         }
@@ -1631,9 +1673,9 @@ NetGraph::derive_node_identities_for_edges (NetGraphNode::edge_iterator e, NetGr
 
     if (bt_count == failed_match) {
       if (tentative) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-        tl::info << indent(depth) << "! rejected branch.";
-#endif
+        if (options ()->debug_netcompare) {
+          tl::info << indent(depth) << "=> rejected branch.";
+        }
         return bt_count;
       }
     } else {
@@ -1642,11 +1684,11 @@ NetGraph::derive_node_identities_for_edges (NetGraphNode::edge_iterator e, NetGr
 
   }
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-  if (! new_nodes) {
-    tl::info << indent(depth) << "! no updates.";
+  if (options ()->debug_netcompare) {
+    if (! new_nodes) {
+      tl::info << indent(depth) << "=> no updates.";
+    }
   }
-#endif
   return new_nodes;
 }
 
@@ -1671,13 +1713,13 @@ NetGraph::derive_node_identities (size_t net_index, size_t depth, size_t n_branc
   size_t other_net_index = n->other_net_index ();
   NetGraphNode *n_other = & data->other->node (other_net_index);
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-  if (! tentative) {
-    tl::info << indent(depth) << "deducing from pair: " << n->net ()->expanded_name () << " vs. " << n_other->net ()->expanded_name ();
-  } else {
-    tl::info << indent(depth) << "tentatively deducing from pair: " << n->net ()->expanded_name () << " vs. " << n_other->net ()->expanded_name ();
+  if (options ()->debug_netcompare) {
+    if (! tentative) {
+      tl::info << indent(depth) << "deducing from pair: " << n->net ()->expanded_name () << " vs. " << n_other->net ()->expanded_name ();
+    } else {
+      tl::info << indent(depth) << "tentatively deducing from pair: " << n->net ()->expanded_name () << " vs. " << n_other->net ()->expanded_name ();
+    }
   }
-#endif
 
   size_t new_nodes = 0;
 
@@ -1722,9 +1764,9 @@ NetGraph::derive_node_identities (size_t net_index, size_t depth, size_t n_branc
 
       size_t bt_count = derive_node_identities_for_edges (e, ee, e_other, ee_other, net_index, other_net_index, depth, n_branch, tentative, with_ambiguous, data);
       if (bt_count == failed_match) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-        tl::info << indent(depth) << "! rejected pair.";
-#endif
+        if (options ()->debug_netcompare) {
+          tl::info << indent(depth) << "=> rejected pair.";
+        }
         return bt_count;
       } else {
         new_nodes += bt_count;
@@ -1733,9 +1775,9 @@ NetGraph::derive_node_identities (size_t net_index, size_t depth, size_t n_branc
     } else if (tentative) {
       //  in tentative mode an exact match is required: no having the same edges for a node disqualifies the node
       //  as matching.
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << indent(depth) << "! rejected pair for missing edge.";
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << indent(depth) << "=> rejected pair for missing edge.";
+      }
       return failed_match;
     }
 
@@ -1758,9 +1800,9 @@ NetGraph::derive_node_identities (size_t net_index, size_t depth, size_t n_branc
 
       NetGraphNode::edge_iterator e = n->find_edge (e_other->first);
       if (e == n->end ()) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-        tl::info << indent(depth) << "! rejected pair for missing edge.";
-#endif
+        if (options ()->debug_netcompare) {
+          tl::info << indent(depth) << "=> rejected pair for missing edge.";
+        }
         return failed_match;
       }
 
@@ -1770,11 +1812,11 @@ NetGraph::derive_node_identities (size_t net_index, size_t depth, size_t n_branc
 
   }
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-  if (! tentative && new_nodes > 0) {
-    tl::info << indent(depth) << "finished pair deduction: " << n->net ()->expanded_name () << " vs. " << n_other->net ()->expanded_name () << " with " << new_nodes << " new pairs";
+  if (options ()->debug_netcompare) {
+    if (! tentative && new_nodes > 0) {
+      tl::info << indent(depth) << "=> finished pair deduction: " << n->net ()->expanded_name () << " vs. " << n_other->net ()->expanded_name () << " with " << new_nodes << " new pairs";
+    }
   }
-#endif
 
   return new_nodes;
 }
@@ -1855,17 +1897,18 @@ static bool net_names_are_different (const db::Net *a, const db::Net *b)
 size_t
 NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *> &nodes, std::vector<const NetGraphNode *> &other_nodes, size_t depth, size_t n_branch, TentativeNodeMapping *tentative, bool with_ambiguous, CompareData *data)
 {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-  std::string indent_s = indent (depth);
-  indent_s += "*" + tl::to_string (n_branch) + " ";
-#endif
+  std::string indent_s;
+  if (options ()->debug_netcompare) {
+    indent_s = indent (depth);
+    indent_s += "*" + tl::to_string (n_branch) + " ";
+  }
 
   size_t new_nodes = 0;
 
   if (depth > data->max_depth) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-    tl::info << indent_s << "max. depth exhausted (" << depth + 1 << ">" << data->max_depth << ")";
-#endif
+    if (options ()->debug_netcompare) {
+      tl::info << indent_s << "max. depth exhausted (" << depth + 1 << ">" << data->max_depth << ")";
+    }
     return failed_match;
   }
 
@@ -1881,9 +1924,9 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
 
       TentativeNodeMapping::map_pair (tentative, this, ni, data->other, other_ni);
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << indent_s << "deduced match (singular): " << nodes.front ()->net ()->expanded_name () << " vs. " << other_nodes.front ()->net ()->expanded_name ();
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << indent_s << "deduced match (singular): " << nodes.front ()->net ()->expanded_name () << " vs. " << other_nodes.front ()->net ()->expanded_name ();
+      }
       if (data->logger && ! tentative) {
         if (! (node (ni) == data->other->node (other_ni))) {
           //  this is a mismatch but we continue, because that is the only candidate
@@ -2030,9 +2073,9 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
         //  their names differ -> this favors net matching by name
 
         if (tentative && ! data->dont_consider_net_names && net_names_are_different ((*nr->n1)->net (), (*nr->n2)->net ())) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-          tl::info << indent_s << "rejecting pair as names are not identical: " << (*nr->n1)->net ()->expanded_name () << " vs. " << (*nr->n2)->net ()->expanded_name ();
-#endif
+          if (options ()->debug_netcompare) {
+            tl::info << indent_s << "rejecting pair as names are not identical: " << (*nr->n1)->net ()->expanded_name () << " vs. " << (*nr->n2)->net ()->expanded_name ();
+          }
           return failed_match;
         }
 
@@ -2044,9 +2087,9 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
 
         TentativeNodeMapping::map_pair (tentative, this, ni, data->other, other_ni);
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-        tl::info << indent_s << "deduced match (singular): " << (*nr->n1)->net ()->expanded_name () << " vs. " << (*nr->n2)->net ()->expanded_name ();
-#endif
+        if (options ()->debug_netcompare) {
+          tl::info << indent_s << "deduced match (singular): " << (*nr->n1)->net ()->expanded_name () << " vs. " << (*nr->n2)->net ()->expanded_name ();
+        }
         if (data->logger && ! tentative) {
           if (! (node (ni) == data->other->node (other_ni))) {
             //  this is a mismatch, but we continue with this
@@ -2086,16 +2129,16 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
 
     } else if (nr->num * n_branch > data->max_n_branch) {
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << indent_s << "max. complexity exhausted (" << nr->num << "*" << n_branch << ">" << data->max_n_branch << ") - mismatch.";
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << indent_s << "max. complexity exhausted (" << nr->num << "*" << n_branch << ">" << data->max_n_branch << ") - mismatch.";
+      }
       return failed_match;
 
     } else {
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << indent_s << "analyzing ambiguity group with " << nr->num << " members";
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << indent_s << "analyzing ambiguity group with " << nr->num << " members";
+      }
 
       //  sort the ambiguity group such that net names match best
 
@@ -2152,16 +2195,16 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
             TentativeNodeMapping::map_pair_from_unknown (&tn, this, ni, data->other, other_ni);
 
             //  try this candidate in tentative mode
-#if defined(PRINT_DEBUG_NETCOMPARE)
-            tl::info << indent_s << "trying in tentative mode: " << (*i1)->net ()->expanded_name () << " vs. " << (*i2)->net ()->expanded_name ();
-#endif
+            if (options ()->debug_netcompare) {
+              tl::info << indent_s << "trying in tentative mode: " << (*i1)->net ()->expanded_name () << " vs. " << (*i2)->net ()->expanded_name ();
+            }
             size_t bt_count = derive_node_identities (ni, depth + 1, nr->num * n_branch, &tn, with_ambiguous, data);
 
             if (bt_count != failed_match) {
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-              tl::info << indent_s << "match found";
-#endif
+              if (options ()->debug_netcompare) {
+                tl::info << indent_s << "match found";
+              }
               //  we have a match ...
 
               if (any) {
@@ -2185,9 +2228,9 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
           }
 
           if (! any && tentative) {
-#if defined(PRINT_DEBUG_NETCOMPARE)
-            tl::info << indent_s << "mismatch.";
-#endif
+            if (options ()->debug_netcompare) {
+              tl::info << indent_s << "mismatch.";
+            }
             //  a mismatch - stop here.
             return failed_match;
           }
@@ -2207,13 +2250,13 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
 
           TentativeNodeMapping::map_pair (tentative, this, ni, data->other, other_ni);
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-          if (equivalent_other_nodes.has_attribute (p->second)) {
-            tl::info << indent_s << "deduced ambiguous match: " << p->first->net ()->expanded_name () << " vs. " << p->second->net ()->expanded_name ();
-          } else {
-            tl::info << indent_s << "deduced match: " << p->first->net ()->expanded_name () << " vs. " << p->second->net ()->expanded_name ();
+          if (options ()->debug_netcompare) {
+            if (equivalent_other_nodes.has_attribute (p->second)) {
+              tl::info << indent_s << "deduced ambiguous match: " << p->first->net ()->expanded_name () << " vs. " << p->second->net ()->expanded_name ();
+            } else {
+              tl::info << indent_s << "deduced match: " << p->first->net ()->expanded_name () << " vs. " << p->second->net ()->expanded_name ();
+            }
           }
-#endif
           if (data->logger) {
             bool ambiguous = equivalent_other_nodes.has_attribute (p->second);
             if (ambiguous) {
@@ -2249,9 +2292,9 @@ NetGraph::derive_node_identities_from_node_set (std::vector<const NetGraphNode *
 
       }
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << indent_s << "finished analysis of ambiguity group with " << nr->num << " members";
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << indent_s << "finished analysis of ambiguity group with " << nr->num << " members";
+      }
 
     }
 
@@ -2516,9 +2559,9 @@ NetlistComparer::compare (const db::Netlist *a, const db::Netlist *b) const
 
     if (all_subcircuits_verified (ca, verified_circuits_a) && all_subcircuits_verified (cb, verified_circuits_b)) {
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << "treating circuit: " << ca->name () << " vs. " << cb->name ();
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << "treating circuit: " << ca->name () << " vs. " << cb->name ();
+      }
       if (mp_logger) {
         mp_logger->begin_circuit (ca, cb);
       }
@@ -2835,9 +2878,7 @@ NetlistComparer::compare_circuits (const db::Circuit *c1, const db::Circuit *c2,
     g2.identify (ni2, ni1);
   }
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
   int iter = 0;
-#endif
 
   //  two passes: one without ambiguities, the second one with
 
@@ -2845,20 +2886,20 @@ NetlistComparer::compare_circuits (const db::Circuit *c1, const db::Circuit *c2,
 
   for (int pass = 0; pass < 2; ++pass) {
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-    if (pass > 0) {
-      tl::info << "including ambiguous nodes now.";
+    if (options ()->debug_netcompare) {
+      if (pass > 0) {
+        tl::info << "including ambiguous nodes now.";
+      }
     }
-#endif
 
     good = true;
     while (true) {
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
       ++iter;
-      tl::info << "new compare iteration #" << iter;
-      tl::info << "deducing from present nodes ...";
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << "new compare iteration #" << iter;
+        tl::info << "deducing from present nodes ...";
+      }
 
       size_t new_identities = 0;
 
@@ -2877,18 +2918,18 @@ NetlistComparer::compare_circuits (const db::Circuit *c1, const db::Circuit *c2,
           size_t ni = g1.derive_node_identities (i1 - g1.begin (), 0, 1, 0 /*not tentative*/, pass > 0 /*with ambiguities*/, &data);
           if (ni > 0 && ni != failed_match) {
             new_identities += ni;
-#if defined(PRINT_DEBUG_NETCOMPARE)
-            tl::info << ni << " new identities.";
-#endif
+            if (options ()->debug_netcompare) {
+              tl::info << ni << " new identities.";
+            }
           }
 
         }
 
       }
 
-#if defined(PRINT_DEBUG_NETCOMPARE)
-      tl::info << "checking topological identity ...";
-#endif
+      if (options ()->debug_netcompare) {
+        tl::info << "checking topological identity ...";
+      }
 
       //  derive new identities through topology: first collect all nets with the same topological signature
 
@@ -2934,9 +2975,9 @@ NetlistComparer::compare_circuits (const db::Circuit *c1, const db::Circuit *c2,
       size_t ni = g1.derive_node_identities_from_node_set (nodes, other_nodes, 0, 1, 0 /*not tentative*/, pass > 0 /*with ambiguities*/, &data);
       if (ni > 0 && ni != failed_match) {
         new_identities += ni;
-#if defined(PRINT_DEBUG_NETCOMPARE)
-        tl::info << ni << " new identities.";
-#endif
+        if (options ()->debug_netcompare) {
+          tl::info << ni << " new identities.";
+        }
       }
 
       if (new_identities == 0) {
diff --git a/src/lay/lay/layApplication.cc b/src/lay/lay/layApplication.cc
index 0d5024e9f..4b8004b8c 100644
--- a/src/lay/lay/layApplication.cc
+++ b/src/lay/lay/layApplication.cc
@@ -1283,14 +1283,6 @@ ApplicationBase::get_config_names () const
   return names;
 }
 
-bool
-ApplicationBase::special_app_flag (const std::string &name)
-{
-  // TODO: some more elaborate scheme?
-  const char *env = getenv (("KLAYOUT_" + name).c_str ());
-  return (env && *env);
-}
-
 // --------------------------------------------------------------------------------
 //  GuiApplication implementation
 
diff --git a/src/lay/lay/layApplication.h b/src/lay/lay/layApplication.h
index 8ef31e2d5..5bd45fa6c 100644
--- a/src/lay/lay/layApplication.h
+++ b/src/lay/lay/layApplication.h
@@ -198,16 +198,6 @@ public:
    */
   std::vector<std::string> get_config_names () const;
 
-  /**
-   *  @brief Gets a value indicating whether the give special application flag is set
-   *
-   *  Special application flags are ways to introduce debug or flags for special
-   *  use cases. Such flags have a name and currently are controlled externally by
-   *  an environment variable called "KLAYOUT_x" where x is the name. If that
-   *  variable is set and the value is non-empty, the flag is regarded set.
-   */
-  bool special_app_flag (const std::string &name);
-
   /**
    *  @brief Return a reference to the Ruby interpreter
    */
diff --git a/src/lay/lay/laySystemPaths.cc b/src/lay/lay/laySystemPaths.cc
index 719c41090..708f1ed45 100644
--- a/src/lay/lay/laySystemPaths.cc
+++ b/src/lay/lay/laySystemPaths.cc
@@ -24,6 +24,7 @@
 #include "laySystemPaths.h"
 #include "tlFileUtils.h"
 #include "tlString.h"
+#include "tlEnv.h"
 
 #include <QDir>
 #include <QFileInfo>
@@ -31,32 +32,17 @@
 
 #ifdef _WIN32
 #  include <windows.h>
-#elif __APPLE__
-#  include <libproc.h>
-#  include <unistd.h>
-#else
-#  include <unistd.h>
 #endif
 
-#include <cstdlib>
-
 namespace lay
 {
 
 std::string 
 get_appdata_path ()
 {
-#ifdef _WIN32
-  wchar_t *env = _wgetenv (L"KLAYOUT_HOME");
-  if (env) {
-    return tl::to_string (QString ((const QChar *) env));
+  if (tl::has_env ("KLAYOUT_HOME")) {
+    return tl::get_env ("KLAYOUT_HOME");
   }
-#else
-  char *env = getenv ("KLAYOUT_HOME");
-  if (env) {
-    return (tl::system_to_string (env));
-  }
-#endif
 
   QDir appdata_dir = QDir::homePath ();
   QString appdata_folder;
@@ -138,23 +124,14 @@ get_klayout_path ()
 
     //  generate the klayout path: the first component is always the appdata path
     klayout_path.push_back (get_appdata_path ());
-#ifdef _WIN32
-    wchar_t *env = _wgetenv (L"KLAYOUT_PATH");
-    if (env) {
-      split_path (tl::to_string (QString ((const QChar *) env)), klayout_path);
+
+    std::string env = tl::get_env ("KLAYOUT_PATH");
+    if (! env.empty ()) {
+      split_path (env, klayout_path);
     } else {
       get_other_system_paths (klayout_path);
       klayout_path.push_back (tl::get_inst_path ());
     }
-#else
-    char *env = getenv ("KLAYOUT_PATH");
-    if (env) {
-      split_path (tl::system_to_string (env), klayout_path);
-    } else {
-      get_other_system_paths (klayout_path);
-      klayout_path.push_back (tl::get_inst_path ());
-    }
-#endif
 
     return klayout_path;
 
@@ -164,23 +141,7 @@ get_klayout_path ()
 std::string
 salt_mine_url ()
 {
-  const std::string default_url ("http://sami.klayout.org/repository.xml");
-
-#ifdef _WIN32
-  wchar_t *env = _wgetenv (L"KLAYOUT_SALT_MINE");
-  if (env) {
-    return tl::to_string (QString ((const QChar *) env));
-  } else {
-    return default_url;
-  }
-#else
-  char *env = getenv ("KLAYOUT_SALT_MINE");
-  if (env) {
-    return (tl::system_to_string (env));
-  } else {
-    return default_url;
-  }
-#endif
+  return tl::get_env ("KLAYOUT_SALT_MINE", "http://sami.klayout.org/repository.xml");
 }
 
 }
diff --git a/src/plugins/tools/xor/lay_plugin/layXORToolDialog.cc b/src/plugins/tools/xor/lay_plugin/layXORToolDialog.cc
index ccb55afed..e4597edce 100644
--- a/src/plugins/tools/xor/lay_plugin/layXORToolDialog.cc
+++ b/src/plugins/tools/xor/lay_plugin/layXORToolDialog.cc
@@ -35,6 +35,7 @@
 #include "tlTimer.h"
 #include "tlProgress.h"
 #include "tlThreadedWorkers.h"
+#include "tlEnv.h"
 #include "tlExceptions.h"
 #include "tlMath.h"
 #include "layCellView.h"
@@ -1085,7 +1086,7 @@ XORToolDialog::run_xor ()
 
   bool summarize = mp_ui->summarize_cb->isChecked ();
   //  TODO: make this a user interface feature later
-  bool process_el = lay::ApplicationBase::instance ()->special_app_flag ("ALWAYS_DO_XOR");
+  bool process_el = tl::app_flag ("always-do-xor");
 
   int cv_index_a = mp_ui->layouta->current_cv_index ();
   int cv_index_b = mp_ui->layoutb->current_cv_index ();
diff --git a/src/tl/tl/tl.pro b/src/tl/tl/tl.pro
index c63c2ec55..7ab83679f 100644
--- a/src/tl/tl/tl.pro
+++ b/src/tl/tl/tl.pro
@@ -46,7 +46,8 @@ SOURCES = \
     tlList.cc \
     tlEquivalenceClusters.cc \
     tlUniqueName.cc \
-    tlRecipe.cc
+    tlRecipe.cc \
+    tlEnv.cc
 
 HEADERS = \
     tlAlgorithm.h \
@@ -103,7 +104,8 @@ HEADERS = \
     tlEquivalenceClusters.h \
     tlUniqueName.h \
     tlRecipe.h \
-    tlSelect.h
+    tlSelect.h \
+    tlEnv.h
 
 equals(HAVE_CURL, "1") {
 
diff --git a/src/tl/tl/tlEnv.cc b/src/tl/tl/tlEnv.cc
new file mode 100644
index 000000000..9b3e03e89
--- /dev/null
+++ b/src/tl/tl/tlEnv.cc
@@ -0,0 +1,85 @@
+
+/*
+
+  KLayout Layout Viewer
+  Copyright (C) 2006-2020 Matthias Koefferlein
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+*/
+
+
+#include "tlEnv.h"
+#include "tlString.h"
+
+#include <string>
+
+#ifdef _WIN32
+#  include <windows.h>
+#elif __APPLE__
+#  include <libproc.h>
+#  include <unistd.h>
+#else
+#  include <unistd.h>
+#endif
+
+namespace tl
+{
+
+std::string get_env (const std::string &name, const std::string &def_value)
+{
+#ifdef _WIN32
+  std::wstring wname = tl::to_wstring (name);
+  wchar_t *env = _wgetenv (wname.c_str ());
+  if (env) {
+    return tl::to_string (QString ((const QChar *) env));
+  } else {
+    return def_value;
+  }
+#else
+  char *env = getenv (name.c_str ());
+  if (env) {
+    return tl::system_to_string (env);
+  } else {
+    return def_value;
+  }
+#endif
+}
+
+bool has_env (const std::string &name)
+{
+#ifdef _WIN32
+  std::wstring wname = tl::to_wstring (name);
+  wchar_t *env = _wgetenv (wname.c_str ());
+  return env != 0;
+#else
+  char *env = getenv (name.c_str ());
+  return env != 0;
+#endif
+}
+
+bool app_flag (const std::string &name)
+{
+  std::string env_name = std::string ("KLAYOUT_") + tl::replaced (tl::to_upper_case (name), "-", "_");
+
+  int v = 0;
+  std::string vs = get_env (env_name);
+  tl::Extractor ex (vs.c_str ());
+  return ex.try_read (v) && v != 0;
+}
+
+} // namespace tl
+
+
diff --git a/src/tl/tl/tlEnv.h b/src/tl/tl/tlEnv.h
new file mode 100644
index 000000000..898ec142c
--- /dev/null
+++ b/src/tl/tl/tlEnv.h
@@ -0,0 +1,65 @@
+
+/*
+
+  KLayout Layout Viewer
+  Copyright (C) 2006-2020 Matthias Koefferlein
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+*/
+
+
+#ifndef HDR_tlAppFlags
+#define HDR_tlAppFlags
+
+#include "tlCommon.h"
+
+#include <string>
+
+namespace tl
+{
+
+/**
+ *  @brief Gets the value for the given environment variable
+ *
+ *  If the environment variable is not set, the default value will be returned.
+ */
+std::string TL_PUBLIC get_env (const std::string &name, const std::string &def_value = std::string ());
+
+/**
+ *  @brief Gets the value if the given environment variable is set
+ */
+bool TL_PUBLIC has_env (const std::string &name);
+
+/**
+ *  @brief Gets an application flag with the given name
+ *
+ *  This feature is supposed to deliver special flags for debugging etc.
+ *  By using a central access point for these settings, it will be easy to provide
+ *  different implementations later.
+ *
+ *  Currently, application flags are derived by checking whether a corresponding
+ *  environment variable exists. Names like "a-b" are translated into "KLAYOUT_A_B"
+ *  for the environment variable.
+ *
+ *  If the corresponding variable exists and does not have a value of "0", true
+ *  is returned from this function.
+ */
+bool TL_PUBLIC app_flag (const std::string &name);
+
+}
+
+#endif
+
diff --git a/src/tl/tl/tlExpression.cc b/src/tl/tl/tlExpression.cc
index 1d26b061b..28cb07d69 100644
--- a/src/tl/tl/tlExpression.cc
+++ b/src/tl/tl/tlExpression.cc
@@ -26,6 +26,7 @@
 #include "tlString.h"
 #include "tlGlobPattern.h"
 #include "tlFileUtils.h"
+#include "tlEnv.h"
 
 #include <map>
 #include <vector>
@@ -35,7 +36,6 @@
 #define _USE_MATH_DEFINES // for MSVC
 #include <math.h>
 #include <string.h>
-#include <stdlib.h>
 #include <ctype.h>
 
 //  Suggestions for further functions:
@@ -2800,9 +2800,9 @@ env_f (const ExpressionParserContext &context, tl::Variant &out, const std::vect
     throw EvalError (tl::to_string (tr ("'env' function expects exactly two arguments")), context);
   }
 
-  const char *env = getenv (vv [0].to_string ());
-  if (env) {
-    out = env;
+  const char *vn = vv [0].to_string ();
+  if (tl::has_env (vn)) {
+    out = tl::get_env (vn);
   } else {
     out = tl::Variant ();
   }
diff --git a/src/tl/tl/tlLog.cc b/src/tl/tl/tlLog.cc
index 258e793a3..1ada55bf2 100644
--- a/src/tl/tl/tlLog.cc
+++ b/src/tl/tl/tlLog.cc
@@ -23,16 +23,12 @@
 
 #include "tlLog.h"
 #include "tlString.h"
+#include "tlEnv.h"
 
 #include <stdio.h>
 #if !defined(_MSC_VER)
 #  include <unistd.h>
 #endif
-#include <stdlib.h>
-
-#if defined(_WIN32)
-#  include <windows.h>
-#endif
 
 namespace tl
 {
@@ -42,21 +38,9 @@ namespace tl
 
 static int default_verbosity ()
 {
-  const char *verbosity_str = 0;
-
-#if defined(_WIN32)
-  const wchar_t *verbosity_wstr = _wgetenv (L"KLAYOUT_VERBOSITY");
-  std::string vs;
-  if (verbosity_wstr) {
-    vs = tl::to_string (std::wstring (verbosity_wstr));
-    verbosity_str = vs.c_str ();
-  }
-#else
-  verbosity_str = getenv ("KLAYOUT_VERBOSITY");
-#endif
-
   int verbosity = 0;
-  if (verbosity_str) {
+  std::string verbosity_str = tl::get_env ("KLAYOUT_VERBOSITY");
+  if (! verbosity_str.empty ()) {
     try {
       tl::from_string (verbosity_str, verbosity);
     } catch (...) {
diff --git a/src/tl/tl/tlUnitTest.cc b/src/tl/tl/tlUnitTest.cc
index 8a719b5fb..f0dd8c7e3 100644
--- a/src/tl/tl/tlUnitTest.cc
+++ b/src/tl/tl/tlUnitTest.cc
@@ -24,6 +24,7 @@
 #include "tlFileUtils.h"
 #include "tlTimer.h"
 #include "tlStream.h"
+#include "tlEnv.h"
 
 #include <cmath>
 
@@ -85,8 +86,8 @@ void set_debug_mode (bool f)
 
 std::string testsrc ()
 {
-  const char *ts = getenv ("TESTSRC");
-  if (! ts) {
+  std::string ts = tl::get_env ("TESTSRC");
+  if (ts.empty ()) {
     throw tl::Exception ("TESTSRC undefined");
   }
   return ts;
@@ -104,8 +105,8 @@ std::string testsrc_private ()
 std::string testtmp ()
 {
   //  Ensures the test temp directory is present
-  const char *tt = getenv ("TESTTMP");
-  if (! tt) {
+  std::string tt = tl::get_env ("TESTTMP");
+  if (tt.empty ()) {
     throw tl::Exception ("TESTTMP undefined");
   }
   return tt;
diff --git a/src/tl/unit_tests/tlExpression.cc b/src/tl/unit_tests/tlExpression.cc
index 7bbb7dcc5..751a3e3a3 100644
--- a/src/tl/unit_tests/tlExpression.cc
+++ b/src/tl/unit_tests/tlExpression.cc
@@ -24,8 +24,8 @@
 #include "tlExpression.h"
 #include "tlVariantUserClasses.h"
 #include "tlUnitTest.h"
+#include "tlEnv.h"
 
-#include <stdlib.h>
 #define _USE_MATH_DEFINES // for MSVC
 #include <math.h>
 
@@ -834,7 +834,7 @@ TEST(6)
   v = e.parse ("env('HJASK')").execute ();
   EXPECT_EQ (v.to_string (), std::string ("nil"));
   v = e.parse ("env('PATH')").execute ();
-  EXPECT_EQ (v.to_string (), std::string (getenv ("PATH")));
+  EXPECT_EQ (v.to_string (), tl::get_env ("PATH"));
   v = e.parse ("absolute_path('./x.gds')").execute ();
   // EXPECT_EQ (v.to_string (), std::string ()); // not universal
   v = e.parse ("absolute_file_path('./x.gds')").execute ();