From Tcl 8.5 [http://wiki.tcl.tk/10630], [expr] operator for list inclusion test. ====== if {$el in $list} ... ====== is equivalent to, but much nicer than ====== if {[lsearch -exact $list $el] >= 0} ... ====== <> The negation ("not in") is [ni]. So 8.5 Tcl really makes us knights who say 'ni'... For users of earlier versions, the following little helper comes in handy: ====== proc in {list el} {expr [lsearch -exact $list $el] >= 0}} ... if [in $list $el] ... ====== - [rs] 2007-04-26 ---- Let's see - so it would be something like: ====== set el Mon set list [list Mon Tue Wed Thu Fri Sat Sun] if {$el in $list} { puts "Valid day abbreviation" } else { puts "Invalid day abbreviation" } ====== <> Operator