#!/usr/bin/perl

use Carp;

eval {
    local $SIG{ALRM} = sub { croak "timed out" };
    alarm 3;

    # ...
    
    # have it hang in line 12
    my $s = <STDIN>;

    # ...
    
    alarm 0;
};

print "$@\n" if $@;

##</code><code>##

timed out at ./645816.pl line 6
        main::__ANON__('ALRM') called at ./645816.pl line 12
        eval {...} called at ./645816.pl line 12
        eval {...} called at ./645816.pl line 5