Re: regexp: non-capturing grouping in replacement possible?

You need look-around assertions, not non-capturing groups. See perlre, search for positive look-ahead assertion and zero-width positive look-behind assertion.

A substitution substitutions not only the captured part of the string, but the matched part of the string. Using zero-width assertion you can reduce the matched part of the string to the captured part.

Comment on Re: regexp: non-capturing grouping in replacement possible?

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Re^2: regexp: non-capturing grouping in replacement possible? by diweooy (Novice) on Nov 26, 2009 at 13:11 UTC
I forgot to mention that I tried it but either I am doing something wrong or ...: `$str =~ s/(?=hello kitty )(\d+)/sprintf "%d", $1/e;` [download] does not do anything. it is probably me but I don't see it.	[reply] [d/l]
Re^3: regexp: non-capturing grouping in replacement possible? by happy.barney (Friar) on Nov 26, 2009 at 13:27 UTC
?= is look ahead. try ?<= (look behind)	[reply]
Re^4: regexp: non-capturing grouping in replacement possible? by moritz (Cardinal) on Nov 26, 2009 at 14:23 UTC
That's right. The regex engine walks the string from left to right, so looking left of a pattern is a look-behind, looking right of a pattern is a look-ahead.	[reply]
Re^4: regexp: non-capturing grouping in replacement possible? by diweooy (Novice) on Nov 26, 2009 at 14:26 UTC
thanks :). working great. `$str =~ s/^(?<=hello kitty )(\d\d)(?=x\d+.)/sprintf "%d", $1/e;;`	[reply] [d/l]