#!/usr/bin/perl
use threads;
use Thread::Semaphore;

sub bad{
	
	sub mysub{
		print "my sub : $1 $2\n";
	}
	$a="Hi there and hi there.\n";
	$a =~ s/(\w+ \w+)(?{mysub();})//gi ;
}


	
sub mythread
{
	print "begin\n";
	print "end\n";
}
					

bad();

my $thr = threads->new(\&mythread);
@r=$thr ->join();

__END__

##</code><code>##

  ./testthread.pl 
my sub : Hi there 
my sub : and hi 
begin
end

*** glibc detected *** /usr/bin/perl: double free or corruption (!prev): 0x08271ce8 ***