Here's my implementation -
$text =~ s/(?<=\b)\n(?=\n\b)//g;

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Consider the string below - 
This is line1\n
\n
line3\n
\n
\n

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What the regex will do is to get rid of the '\n' at the end of line1, which is followed by another \n and a word boundary.

This solution is similar to qq's answer above, but with subtle differences. qq's solution will replace two consecutive \n's with a single \n, while my solution will get rid of the first \n.

In reply to Re: remove single blank lines? by Roger
in thread remove single blank lines? by aloomens

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