Here is my sample code reworked to use a tied array (not all the necessary features of a tied array are implemented here FETCHSIZE and STORESIZE may not be very useful as written-- I just wanted to try the basics of tie and get this example to work a little less clumsily). Thanks to ar0n for suggesting tie in the first place, to ar0n and broquaint for helping me fix a bug in this code. Note that you can also export the $Concat variable in the package to avoid having to package qualify it in Main, but I think I prefer it how it is. 
#!/usr/bin/perl -w
use strict;
use Tk;

my @bit;
tie @bit, 'Bitters';
   
my $mw = Tk::MainWindow->new();

my $entry =
    $mw->Label( -textvariable => \$Bitters::Concat,
        )->
    pack( -expand => 'y',
      );

my $foo_button = 
    $mw->Button( -text => "Bit One",
         -command => sub { flip( $bit[1] );}
         )->pack();

my $bar_button =
    $mw->Button( -text => "Bit Zero",
         -command => sub { flip( $bit[0] );}
         )->pack();

print "MainLoop\n";
MainLoop();

sub flip
{
   $_[0] = ( $_[0] eq 'x' ) ? 'y' : 'x';
}
    
{ package Bitters;

  use vars qw( $Concat );

  sub TIEARRAY {
      my $class = shift;
      
      my $self = { ARRAY => ['x','x'] };
      bless $self, $class;

      $self->update_concatenation();

      return $self;
  }

sub FETCH 
{
    my($self,$idx) = @_;
    return $self->{ARRAY}[$idx];
}

sub FETCHSIZE
{
    my $self = shift;
    return $self->{ARRAY}+0;
}

sub STORESIZE
{
    print "STORESIZE ignored\n";
}

sub STORE 
{
    my($self, $idx, $value) = @_;
    print "[STORE $value at $idx]\n";

    $self->{ARRAY}[$idx] = $value;
    $self->update_concatenation();

    return $self->{ARRAY}[$idx];
}      

sub update_concatenation
{
    my $self = shift;
    $Concat = $self->{ARRAY}[0] . $self->{ARRAY}[1];
    print "$Concat\n";
}

}#end_package Bitters;

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In reply to (ichimunki) Re: Updating concatenated text on a Menubutton by ichimunki
in thread Updating concatenated text on a Menubutton by Kahlua_II

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