You can use quotemeta function or \Q .. \E in your regular expression -
if ($text =~ /.*\Q$stub\E.*/s)
{ 
  #do something
}

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Updated: I thought it might be useful for you to have a read of the perlre documentation on CPAN here. Look for quotemeta.

In reply to Re: Matching brackets in Regular Expression by Roger
in thread Matching brackets in Regular Expression by Levan

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