Move the loop out of the regex.

$_="17341234";
1 while s/(.)(...)\1/A$2B/;
print "$_\n"

[download]

Added: Also - if you need to prevent restarting the regex for some reason, you can add some additional code and still get that. The addition of the eval block and the substr() might be more expensive than starting over - I'll leave that to someone else to benchmark. (and on varying size data)

$_="17341234";
$r = 0;
1 while substr($_,$r) =~ s/(.)(...)\1(?{local $r = pos() - 3})/A$2B/;
print "$_\n"

[download]

In reply to Re: Replace zero-width grouping? by diotalevi
in thread Replace zero-width grouping? by tinypig

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