You might want to try forming the words into an optimized regex. Also, you might want to make sure the strings are quotemeta()ed, in case they contain regex characters.

my $regex = join '|', map quotemeta($_), @strings;
$regex = qr/$regex/;
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As far as optimizing goes, since Perl uses NFA (not DFA), you'll get an efficiency boost:

/out|this|once|those or|about|bout/

# will work better as

/th(is|ose or)|((a?)b?)out|once/
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Update: you also want to put the smaller stop-words towards the beginning of the regex, if at all possible.

japhy -- Perl and Regex Hacker