in reply to Re^2: Removing double carriage return
in thread Removing double carriage return
From the command line, this replaces 3 or more newlines with 2 newlines or replaces exactly 2 newlines with 1 newline.
perl -i.bak -0777 -pe 's/(\n{3,}|\n\n)/2 == length $1 ? "\n" : "\n\n"/eg' inputfile
Notice that this looks for the longest match first (so that 2 newlines won't match more than 2, i.e. 3 or more).
Update: That could be simplified to:
perl -i.bak -0777 -pe 's/\n+/2 < length $& ? "\n\n" : "\n"/ge' inputfile
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