You need \Q...\E which quotes metacharacters in regexes.

if ($a =~ m/\Q$b\E/)

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See also quotemeta

By the way, $a and $b have a special meaning to Perl (because of their use in sorting) so it's a really bad idea to use them for anything else.

--
<http://dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg

In reply to Re: Regular expression match trouble with "+" by davorg
in thread Regular expression match trouble with "+" by kwyjibo

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