(?=a|b|c)

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I'm not sure how it iterprets exactly, but I think you need actually 
perl -e '$_ = "(b)."; /\([abc]\)/ && do { print "match!\n"; };'

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or 
perl -e '$_ = "(b)."; /\((a|b|c)\)/ && do { print "match!\n"; };'

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In reply to Re: Why does this simple grouping regex not match? by fisher
in thread Why does this simple grouping regex not match? by december

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