in reply to capturing output from open |

Yes. The easiest is to open STDERR to some file before opening the "piped open". You could then read the file afterwards.

see perldoc -f open...

s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e

In Section Seekers of Perl Wisdom