[Richard Suchenwirth] - Here is a little [menu] demo that allows localization for different languages, either at startup (by specifying one of the language codes ''de, en, fr'' as first argument, and on-the-fly while running, by using inlined [msgcat] commands, so the single file is self-contained.
 package require msgcat
 namespace import msgcat::*

 mcset de Language Sprache
 mcset de English  Englisch
 mcset de German   Deutsch
 mcset de French   Franz�sisch

 mcset fr Language Langage
 mcset fr English  Anglais
 mcset fr German   Allemand
 mcset fr French   Francais

 set choice [lindex $argv 0]
 if {[lsearch "en de fr" $choice]>=0} {mclocale $choice}

 proc makeMenu {} {
    catch {destroy .m}
    . config -menu [menu .m]
    menu .m.m2
    .m add cascade -label [mc Language] -menu .m.m2
    foreach {language code} {English en French fr German de} {
	.m.m2 add command -label [mc $language] -command [list reset $code]
    }
 }
 proc reset code {
    mclocale $code
    .m entryconfig 1 -label [mc Language]
    foreach i {1 2 3} label {English French German} {
	.m.m2 entryconfig $i -label [mc $label]
    }
 }
 makeMenu
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[i18n: Writing for the world] - [Arts and crafts of Tcl-Tk programming]