Re^2: A regex that only matches at offset that are multiples of a given N?

In this regex:

fred
(?              
    (?{ pos % 4 != 0 })
    (?!)
)
(....)
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What does this construct do:

(?stuff)
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I can't find anything about that in perlre.

Edit: Ah, the boolean test finally clued me in:

(?(condition)yes-pattern)
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Re^3: A regex that only matches at offset that are multiples of a given N? by smls (Friar) on Feb 15, 2013 at 12:27 UTC
I can't find anything about that in perlre. perlre is not exactly optimized for quickly finding out the meaning of a specific regex construct. Use perlreref for that.	[reply]