Since the if block is only entered about 20000 times, changes there aren't likely to make a big difference.

But yes, seeing what kind of patterns these are would provide some clues. If they are literal strings, for instance, it may be better to not do the qr// but instead do

    if (0 <= index($text, $pattern) && $text =~ /\b$pattern\b/) {
    }
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(the latter bit just to preserve the \b checks).