[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. 
For 4 LOC more, you also get the window title localized ;-)

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 package require msgcat
 namespace import msgcat::*

 mcset de Language Sprache
 mcset de English  Englisch
 mcset de German   Deutsch
 mcset de French   Französisch
 mcset de Test     Versuch

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

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

 proc makeMenu {} {
    . config -menu [menu .m]
    menu .m.m2 -tearoff 0
    .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]
    }
    wm title . [mc Test]
 }
 proc reset code {
    mclocale $code
    .m entryconfig 1 -label [mc Language]
    foreach i {0 1 2} label {English French German} {
        .m.m2 entryconfig $i -label [mc $label]
    }
    wm title . [mc Test]
 }
 makeMenu
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