diff --git a/doc/xschem_man/component_property_syntax.html b/doc/xschem_man/component_property_syntax.html
index b7c63a3a..f64ca1a4 100644
--- a/doc/xschem_man/component_property_syntax.html
+++ b/doc/xschem_man/component_property_syntax.html
@@ -184,6 +184,19 @@ name="mchanged_name" model=\"nmos\" w="20u" l="3u" m="10"
This is mainly used for tedax, where by back annotation a connection to a symbol must be changed.
This notation is faster since xschem does not have to find a pin by string matching.
+
+ TCL ATTRIBUTE SUBSTITUTION
+
+
+ Any attribute and symbol text can be embedded in a tcleval(....) construct, the string inside the
+ parentheses will be passed to the tcl interpreter for evaluation. This allows to use any tcl
+ variable/command/expression. Example:
+ value="tcleval([expr {[info exists ::resval] ? $::resval : {100k}}])"
+ this attribute will set value (example: value of a resistor) to 100k if global tcl variable
+ resval is not set or to the value of resval if set.
+
+
+
diff --git a/doc/xschem_man/symbol_property_syntax.html b/doc/xschem_man/symbol_property_syntax.html
index 97309939..b65bfbad 100644
--- a/doc/xschem_man/symbol_property_syntax.html
+++ b/doc/xschem_man/symbol_property_syntax.html
@@ -458,6 +458,16 @@ verilog_format="xnor #(@risedel , @falldel ) @name ( @@Z , @@A , @@B );"
this expandes to the Verilog global property string of the schematic containing the symbol
+ TCL ATTRIBUTE SUBSTITUTION
+
+
+ Any attribute and symbol text can be embedded in a tcleval(....) construct, the string inside the
+ parentheses will be passed to the tcl interpreter for evaluation. This allows to use any tcl
+ variable/command/expression. Example:
+ spice_ignore="tcleval($::ignore_symbol)"
+ will cause the symbol to be ignored by the spice netlister if the ignore_symbol tcl variable is
+ existing and set to true
+