It's been reported already with no resolution.

You could force the regexp to be recompiled in each thread for now: 

# Globals
my $expensive_re_str =
   ''.qr/([\w.+-]+@(?:[\w-]+\.)+\w{2,5})(?<!\.(?:jsp|asp|jpg|htm)\W/i;
my %expensive_re;

# Workaround for perl bug RT#55600
my $expensive_re =
   $expensive_re{$thread_id} ||= qr/$expensive_re_str/;
my ($mail) = $string =~ m/$expensive_re/;

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In reply to Re: regular expression hanging inside a child thread by ikegami
in thread regular expression hanging inside a child thread by dxxd116

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