I don't think the look-behind assertion and anchor are necessary (the anchor actually causes it to terminate early on certain boundary cases with newlines): 
s/(.{0,79}\S\s+)/$1\n/gm

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... I could be wrong :) 
   MeowChow                                   
               s aamecha.s a..a\u$&owag.print

In reply to (MeowChow) Re2: goto() in regexes by MeowChow
in thread goto() in regexes by japhy

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