use Tk;
use Tk::DialogBox;
use strict;
use warnings;

my $top = new MainWindow(-title => "demo");	
my $save = $top->Button(-text => "Goto line", command => \&process_save)->pack();
my $line_num;
MainLoop;

sub process_save {
	my $dialog = $top->DialogBox(-title => "Save?", -buttons => ["OK", "Cancel"]);
	$dialog->add("Entry", -text => \$line_num)->pack();
	my $response = $dialog->Show();
	print "[$response, $line_num]\n" #in real code, handle the response...
}