I would guess from one of your previous posts that you are asking in the context of Tk. You can do something like this

$widget->bind(q{<KeyPress>}, \&callback);
[download]

and you can get access to the event to find out which key was pressed in the callback() routine. Have a look at the Tk::bind and Tk::Event man pages for more info.

Cheers,

JohnGG