perlhacktips: Note existence of regen/unicode_constants.pl
perlintro: Typo and stop verbatim wrapping
Document \s change for VT, commit 075b9d7d9a6d4473b240a047655e507c8baa6db3
Move (?[]) doc to perlrecharclass

This is a form of bracketed character class, and so should be documented
in the same pod.