Take your "BUT" example and extend it:

perl -e "$_='qwerty'; s/r/print pos(). \"\n\";/e; print $_;

OUTPUT: 

3
qwe1ty

[download]

Note the "1" (one) in the replaced output. Maybe you can go somewhere with this.

In reply to Re^9: Using pos() inside regexp (no /e) by ww
in thread Using pos() inside regexp by braveghost

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