Read up on the function quotemeta.

Alternatively, wrap it with \Q$regexp\E in your regexp like this:

my $text = 'foo bar + \wbaz';
my $re = ' + \w';

if ($text =~ /(\Q$re\E)/) {
        print $1;
} else {
        warn "nothing found\n";

}
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That goes for the same as quotemeta does, just for the regexp.

Mats