use strict;
use warnings;

use Tk;

my $param = '';

my $mw = Tk::MainWindow->new;

$mw->Label(-text=>'Please enter your parameter:')->pack;

$mw->Entry(-textvariable=>\$param)->pack;

$mw->Button(-text=>'Submit (even if no button are needed',
            -command=>sub{
                print "Button was pressed: \$param is now '$param'\n";
            })->pack;

MainLoop();