Hopefully someone who needs to use maps for ttk::entry widgets might find this
useful.  With any luck I'll have transposed it correctly, and it should just work.

''I don't find this very user-friendly. The template doesn't show until you edit a sufficient number of characters. What's worse, a backspace after a fixed character does nothing -- you're forced to step over the character using the mouse or an arrow key. And if you move around a bit you can really get the widget confused. For example, in the second example field I somehow ended up with 999//9/9/9, with backspace refusing to delete anything. You better not use this in any production code just yet...''

----


 #
 # A Tcl/Tk Data Entry poor man's template package.
 # Written by Rob Sciuk of Control-Q Research 2008
 #
 # Usage terms as with the same BSD license as Tcl/Tk.
 # eg: use it for whatever you'd like ... but don't
 # call me when something breaks ;-)
 #
 # data entry package, adds template input ...
 # eg:   {(999) 999-9999}
 #       {9999/99/99}
 #       {99:99:99}
 # note, a <SPACE> will delete the entry ...
 # sample code at bottom.
 #
 namespace eval de {

        # map:  9       digit
        #       A       alpha
        #       X       Alpha numeric
        #       .       sep character (Literal)
        proc fmtChar chr {
                if [string equal "9" $chr] {
                        return digit
                }
                if [string equal "A" $chr] {
                        return alpha
                }
                if [string equal "X" $chr] {
                        return alnum
                }
                return literal
        }

        proc Mapper { map wdg key } {
                if [string equal " " $key] {
                        if [$wdg selection present] {
                                $wdg delete sel.first sel.last
                                return 1
                        }
                        $wdg delete 0 end
                        return 1
                }
                set val [$wdg get]
                set ix [string length $val]
                set mx [string length $map]
                if { $ix >= $mx } {
                        return 0
                }
                set fm [string index $map $ix]
                set tst [fmtChar $fm]
                switch $tst {
                        digit -
                        alpha -
                        alnum {
                                if [string is $tst $key] {
                                        return 1
                                }
                                return 0
                        }
                        literal {
                                while { [string equal literal $tst] == 1 } {
                                        $wdg insert end $fm
                                        incr ix
                                        set fm [string index $map $ix]
                                        set tst [fmtChar $fm]
                                }
                                if [string is $tst $key] {
                                        $wdg insert end $key
                                        return 1
                                }
                                return 0 
                        }
                   }
                   return 1
         }
 }

 # sample usage ...
 package require Tk
 package require Ttk
 ttk::entry .e0 -width 14 -invalid bell \
        -validate key -validatecom [list de::Mapper {(999) 999-9999} %W %S]
 ttk::entry .e1 -width 14 -invalid bell \
        -validate key -validatecom [list de::Mapper {9999/99/99} %W %S]
 ttk::entry .e2 -width 14 -invalid bell \
        -validate key -validatecom [list de::Mapper {99:99:99} %W %S]
 pack .e0
 pack .e1
 pack .e2

----
!!!!!!
%| data+entry map|%
!!!!!!