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

my $mw = MainWindow->new();

my $content = '';
my $entry = $mw->Entry(-textvariable => \$content)->pack();

$entry->bind('<Return>',sub{ 
   my $val = $entry->get;
   print "check with regex here and do what is needed  $val\n" });

$entry->focus;
MainLoop;