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Re^3: substitution in regular expression

by trizen (Hermit)
on Apr 23, 2014 at 22:52 UTC ( #1083484=note: print w/ replies, xml ) Need Help??

in reply to Re^2: substitution in regular expression
in thread substitution in regular expression

Short explanation: (?{...}) means to execute arbitrary Perl code inside a regular expression, and (?!) makes the regex engine to fail and backtrack, trying to match from the last_pos + 1. When it starts matching ABC, it prints it, fails, backtracks and starts matching from B the next three letters, giving us BCD. The process repeats until the internal regex counter reaches the end of the string.

I know, I'm really bad at explaining things to humans, but, fortunately, Athanasius explained this better once.

Please see: Re: RegEx + vs. {1,}

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Re^4: substitution in regular expression
by aeqr (Novice) on Apr 23, 2014 at 23:05 UTC
    Thanks a lot! Very well explained actually. It's a nice trick to know.

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