You don't want to use "word boundary", but rather "boundary". There is no shortcut for boundary, so you'll have to use: 
/(?:(?=\w)(?<!\w)|(?=\W)(?<!\W))($thing)(?:(?<=\w)(?!\w)|(?<=\W)(?!\W)
+)/

[download]
You could also use the (?(...)TRUE|FALSE) assertion to clean that up a bit: 
/(?(?=\w)(?<!\w)|(?<!\W))($thing)(?(?<=\w)(?!\w)|(?!\W))/

[download]
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re: Regex help by japhy
in thread Regex help by Anonymous Monk

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