I'd throw a couple of \b's in there, so it only matches on word boundaries. eg: 
$text =~ s/\b(dog|cat|fox|cow|pig)\b/\n$1/g;

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Otherwise, you'd match stuff like "cowardly" and "pigheaded" ;)

In reply to Re^2: Understanding alternation by McDarren
in thread Understanding alternation by Anonymous Monk

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