#!/usr/bin/perl
use warnings;
use strict;

$SIG{ALRM} = sub { die "timeout!!! alarm\n" };

alarm(5); #start the timer

print "waiting for alarm..hit any key...";
<STDIN>;
print "waiting for another input line";
<STDIN>;
print "past the IO stuff, normal exit\n";

__END__
should see this if no key at all is hit
waiting for alarm..hit any key...timeout!!! alarm