FIRST: here is the perl code/widget that I made which works:

#! /usr/pkg/bin/perl 

 use warnings;
# use diagnostics;

 use Tk;
 use Tk::Entry;


    unshift (@INC , "/usr/pkg/lib/perl5/site_perl/5.30.0/x86_64-netbsd
+-thread-multi/Tk");
    unshift (@INC , "/usr/pkg/lib/perl5/vendor_perl/5.30.0/Cache/Memca
+ched");

    unshift (@INC , "/usr/pkg/lib/perl5/site_perl/5.30.0/Cache");



 $mw = MainWindow -> new();
 $mw -> title ("Listbox");

 @choices = qw /alpha beta charlie delta echo foxtrot hotel india juli
+et kilo lima motel nancy oscar papa quebec radio sierra tango uniform
+ victor whiskey xray yankee zulu oin gloin beorn gandalf elrond eowyn
+/;
 $header_msg = "ENTER a KEY name: ";

my ($search , $oldsearch);

##--------------------------------------------------------------------
+------------##

  &listbox1 (@choices , $header_msg ); ##WORKS!! Make sure the $msg is
+ last element

##--------------------------------------------------------------------
+------------##

MainLoop;


sub listbox1
   {
      my(@choices , $header_msg   );
        $header_msg = pop (@_) ;
        @choices = @_ ;







    my $dialog = $mw -> Label (-text => $header_msg ) -> pack( -side =
+> "top"  );
       $dialog = $mw -> Entry (-textvariable => \$search,             
+             
                             ) -> pack (
                                         -side => "top" , 
                                         -fill => "x"
                                       );  

       $dialog -> bind ( "<KeyPress>" , [\&do_search , Ev ("K" )]  ); 





  #    $mw = $dialog -> Show(); #HMMMMMM... WORKED; so Show() is unnee
+ded?


##############

    $lb = $mw -> Scrolled ("Listbox" , -scrollbars => "se" ,  
                                         -height => 20 ,
                                         -selectforeground => 'orange'
+,
                                         -selectbackground => 'steelbl
+ue4' ,
                            ) -> pack(-side => "top") ;


      $lb -> insert ( "end" , sort @choices  );
                         ### MAKE '@choices' the list of $keys



      my $f = $mw -> Frame( ) -> pack(-side => 'bottom' , -fill => "x"
+  )  ;




        $f -> Button ( -text => "QUIT" , 
                       -background => 'red',
                       #  -relief => 'sunken'
                       -command => sub { ( $mw -> destroy() ) if Tk::E
+xists( $mw ); }
                     ) -> pack (-side => 'bottom' , -fill => "x"  ); 


     $lb   ->  bind( '<Double-1>' , \&get_choice );

   } ## CLOSE listbox1()

##################


sub get_choice
   {
     my $mychoice = $lb -> get( 'active');
     print "\$mychoice = : $mychoice\n\n   ";

   }


sub do_search
   {

     my ($entry , $key) = @_;
     return if ( $key =~ /backspace/  );
     return if ( $oldsearch eq $search  );

     
     my @list = $lb -> get(0 , "end");


     foreach ( 0 .. $#list   )
       {
         if ($list [$_] =~ /^$search/ )
           {
             $lb -> see($_);
             $lb -> selectionClear( 0 , "end"  );
             $lb -> selectionSet ($_);
             last;
           }
       }

    $oldsearch = $search;



   } ## CLOSE do_search()
[download]

WHAT I like about it is it sticks the vars in a listbox with a slider. It also searches. Type in the first letter(s) and it takes you to the matching string. I can see uses elsewhere for such a thing. In this case it is for choosing hash-keys so I can delete Cache::Cache entries/elements
I am curious: Why isnt there a megawidget repository somewhere?