use strict;
use warnings;


my $start;
my $diff;
my $timeout;


sub tst {
    $timeout=shift;
    my $str = "a"x10000;
    $str   .= "b";

    eval {
        local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
        alarm $timeout;
        $str =~ /^ (( a*
                         (?{1})  # dummy code
                     )*)*  $/x;    
        alarm 0;
    };
    if ($@) {
        die unless $@ eq "alarm\n"; # propagate unexpected errors
        die "timed out after $timeout sec :". time();
    }
    else {
        print "normal";
    }

}
tst($_)  for 2;


##</code><code>##

Complex regular subexpression recursion limit (32766) exceeded at /home/lanx/B/PL/PM/timeout_regex.pl line 18.

Compilation segmentation fault at Fri May 30 17:41:48