http://www.perlmonks.org?node_id=1169094


in reply to Re: regex issue
in thread regex issue

A slightly different approach can give you what you are looking for. By using a lookahead, you can do what you want.

$term = 'Dit is het eerste het is niet het laatste Dit'; @captured = $term =~ /\b(\w\w\w)\b(?=.*\1\b)/g; print join ' ', @captured; _____________ Dit het het

The \b are word boudaries (change from letter/number/underscore) to non-letter/number/underscore or vice-versa.

The (?= looks forward for what comes after it, but remembers where it starts.

The \1 is the same as your \g1 (I unfortunately have an older perl.)

The g at the end means capture them all

het appears twice since it is there three times

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Re^3: regex issue
by kroach (Pilgrim) on Aug 03, 2016 at 20:21 UTC
    Small correction, you missed a word-boundary assertion in the look-ahead. The regex should be:
    /\b(\w\w\w)\b(?=.*\b\1\b)/g
    Without the additional \b before \1, three-letter words that are trailing substrings of other words would also match.

      Thanks. I missed that copying from the PC that has perl that I tested this on to this one.

Re^3: regex issue
by Anonymous Monk on Aug 03, 2016 at 19:08 UTC

    Thank you