#!/usr/bin/perl -w
    use Tk;
    use strict;    
   
    my $mw = MainWindow->new;
    my $value = 10;
    $mw->Label(-text => 'Number')->pack;
    my $nmbr = $mw->Entry(-width => 10, -textvariable => \$value);
    $nmbr->pack;  

   
    $mw->Button(
        -text => 'Print',
        -command => sub{do_print($value);}
        )->pack;  
         
   
    MainLoop;      
   
   
    sub do_print
    {
        (my $value) = @_;
        print "Printing number $value\n";
    }