I was unable to get a segfault testing the exact code I posted on either 5.10.1 on CentOS or 5,16,2 on OSX. I only tested it with the strings and regex listed in the code, though.

I hope it's fixed for newer versions, here what I tried for reproduction:

Just taking the code from alarm and embedding (dummy) code into a long running regex

Generally I try to avoid alarm...

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;
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output

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

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

( addicted to the Perl Programming Language)

I also get a core dump on 5.10.1 (CentOS) with that code but not on 5.16.2 (OSX) FWIW.

$ perl baz
Complex regular subexpression recursion limit (32766) exceeded at baz 
+line 18.
timed out after 2 sec :1401464941 at baz line 25.
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This is perl 5, version 16, subversion 2 (v5.16.2) built for darwin-th
+read-multi-2level
(with 3 registered patches, see perl -V for more detail)
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