Well, yes, the constant-width part is a big requirement for using a lookbehind, which is why I devised this method. And I'd expect one regex to be faster than two. But you also bring up the capturing parentheses, which are also an advantage of the one-regex method.
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Jeff[japhy]Pinyan:
Perl,
regex,
and perlhacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;