Quick and dirty:
perl -le '$_="00110011111110111111111111111110"; $m=( sort({length($b)
+<=>length($a)} /(1+)/g ) )[0];s/$m/2 x length $m/e;print'

[download]

Paul

In reply to Re: how to replace a matched pattern in a string with a different pattern of same length? by rev_1318
in thread how to replace a matched pattern in a string with a different pattern of same length? by BhariD

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