It seems to me you are looking for an "event -driven" script. Tk does this, it will enter an "event loop" and watch for various types of events. A real simple example:

#!/usr/bin/perl
use Tk;
my $mw = new Tk::MainWindow;
my $btn = $mw->Button(-text => 'Hit Return')->pack();

# 
# Note that we *usually* bind to the main window, 
#  not the button - it's a focus thing. 
# 
$mw->bind('<Return>', \&_on_rtn);

MainLoop;
exit(0);

sub _on_rtn
    {
        $mw->messageBox(-message=>'Thanx for using the keyboard!');
            }
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