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Answer: How do I find the Nth occurrence of a pattern?

by Roy Johnson (Monsignor)
on Oct 28, 2003 at 20:53 UTC ( #302814=categorized answer: print w/replies, xml ) Need Help??

Q&A > regular expressions > How do I find the Nth occurrence of a pattern? - Answer contributed by Roy Johnson

A recent discussion found this to be the fastest way, and it's pretty slick:
$_='abcabbcabbbbcabcabbcab'; my $n = 3; ## Find the $nth occurrence my $pat = qr/ab+/; ## of this pattern my ($NthMatch) = /(?:.*?($pat)){$n}/; print "Match #$n looks like $NthMatch\n";
The regex is: find the pattern (optionally preceded by something that isn't the pattern) n times. The pattern is in parens, so the final match will be returned.

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