#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = tkinit;

my @employs = ('A'..'Z');
my @active = ();

my $l1 = $mw->Scrolled('Listbox',
       -listvariable => \@employs,
       -scrollbars =>'osow')->pack( -side => 'left' );

my $l2 = $mw->Scrolled('Listbox',
        -listvariable => \@active,
       -scrollbars =>'osow')->pack( -side => 'left',-padx=>10 );

my $button = $mw->Button(-text=>'Print Active',
             -command => sub{ print "@active\n"}
             )->pack(-side=>'left');


$l1->bind( '<ButtonRelease-1>', sub { update( $_[0], $l2 ) } );
$l2->bind( '<ButtonRelease-1>', sub { update1( $_[0], $l1 ) } );

MainLoop;

sub update {
    my ( $src, $dst ) = @_;
    my $index = $src->curselection;
    if ($index) {
        my $value = $src->get($index);
#        print "$value\n";
       @employs = grep { $_ ne $value } @employs;
       push @active, $value;
       @employs = sort @employs;
       @active = sort @active;
    }
}

sub update1 {
    my ( $src, $dst ) = @_;
    my $index = $src->curselection;
    if ($index) {
        my $value = $src->get($index);
#        print "$value\n";
       @active = grep { $_ ne $value } @active;
       push @employs, $value;
       @employs = sort @employs;
       @active = sort @active;
    }
}