You were bitten by negative-over-or-logic. The left side of the | will match what the right side is intended to skip. It has to be something like 
$field =~ s/
  (?<!C(?=.O))   # Look back a character and make sure it's not C-some
+thing-O from there
  (?<!\d(?=.\d)) # Make sure it's also not a digit-something-digit
  (?:\\|\/)      # The something is a slash or backslash
/ & /xgi;

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In reply to Re^2: Regex Question by Roy Johnson
in thread Regex Question by shemp

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