It died on my 5.6.1, but no matter -- just introduce some $1 in there, and it breaks on everything I have (5.8 included):

"japhy" =~ m{
  (
    .
    (?{ "perl" =~ /(.)/; print $1 })
    .
  )
  (?{ print $1 })
}x
[download]

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;