Perl Tk GUI Design Question?

I'm looking for a way to use a bmp or gif as the background of a window. I can't quite figure how I would do that, but I assume it should be possible. Any help?

use Tk;

use strict;

my $mw = MainWindow->new;

$mw->geometry("400x100");

$mw->title("Main Window");

#$mw->Photo('imgbmp',-file=>"F:\\matrix.gif");

#$mw->Label('-image'=>'imgbmp')->pack;

my $info_frame1 = $mw->Frame()->pack(-side => "top");

my $message1;

$message1 = $info_frame1->Entry()->pack(-side => "right");

$message1->focus;

$info_frame1->Label(-text => "Enter Username:")->pack(-side => "right");

my $button1 = $mw->Button(-text => "Open chat window",

-command => \&button1_sub)->pack(-side => "top");

$button1->bind('Tk::Entry','<Return>', \&button1_sub);

$mw->bind('Tk::Entry','<Key-Escape>', sub{exit});

$mw->Button(-text => "Exit", -command => sub{exit})->pack();

my $message;