It's often the result of using the nonsensical if (/.../g) 

$ perl -e'
   $_ = "abc";
   if (/\w/g) {
      CORE::say for /(\w)/g;
   }
'
b
c

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In reply to Re^2: Some odd ambiguity in this regex (updated) by ikegami
in thread Some odd ambiguity in this regex by misterperl

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