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Perl: the Markov chain saw

Re: Replace the nth occurence

by trizen (Hermit)
on Nov 21, 2012 at 10:56 UTC ( #1004895=note: print w/replies, xml ) Need Help??

in reply to Replace the nth occurence

A general solution:
my $nth = 4; my $str = 'a=>bb=>ccc=>dddd=>eeeee=>ffffff'; while ($str =~ /=>/g) { if (--$nth == 0) { substr($str, $-[0], $+[0] - $-[0], '~~|~~'); last; } } print "$str\n";

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Re^2: Replace the nth occurence
by AnomalousMonk (Chancellor) on Nov 21, 2012 at 22:49 UTC

    In the sprit of this, also a generalized approach. No benchmarking done for two regexes used or versus other approaches. Note also that the index of the occurrence of the pattern which will be replaced is now zero-based. (Also: This approach could be generalized yet further by passing either a plain replacement string or a code reference. The string/reference could then be fed as appropriate to one of two  s/// substitutions, one without a /e regex modifier, one with. Code of a replacement reference would have access to all capture variables, etc.) All tests pass.

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