#!/usr/bin/perl -w
                                                                                
use Tk;
                                                                                
use strict;
use warnings;
                                                                                
my $mw = new MainWindow();

$mw->bind( '<KeyPress-Control-a>', sub {print "Button a has been pressed\n"} );
$mw->bind( '<KeyPress-Control-a>', sub {print "Button a has been released\n"} );

MainLoop;

# Produces ...
bad event type or keysym "Control" at
/usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi/Tk/Derived.pm line 469.

# My version of Perl
This is perl, v5.8.0 built for i386-linux-thread-multi