Ah, yes, this is the clever part I was missing: 
  (?<!\\)
  ((?:\\{2})*)

[download]
It makes sure that only unescaped metachars are converted (all preceding escapes are even).
Thanks!

But why is the following an optimization (against my code)?: 
for ($string) {
    $result .= $1 if /\G ([^\\*?]+) /xgcs;

    /\G \\(.) /xgcs && do { $result .= $1;   redo; };
    /\G \*    /xgcs && do { $result .= '?';  redo; };
    /\G \?    /xgcs && do { $result .= '#';  redo; };
}

[download]
If I see it right, both versions try to keep the common case at the beginning and have to walk through the other regexes until the first match. (Besides the 'redo' irritated me until I read in the docs that it doesn't redo do-blocks) But still thank you very much for this too, it is always good to have variations at hand.
-Michael

In reply to Re^2: Replace only unescaped metachars by Anonymous Monk
in thread Replace only unescaped metachars by Anonymous Monk

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