Relevent nodes:
How does one redirect STDERR to a file? ((Filehandle, redirection, logging)) & Getting STDERR to write to STDOUT?

Super Search is your friend
Update:
Just making my other node redundant and gathering data

Filehandle Filter cuts more to the chase and if you go to Filter::Handle by brott and read the doc there's even an example on how to put a Filehandle's output to a string and at that point, an array is trivial.

And More:This recent node shows some clues as well: The art of error handling
-lemming
p.s. Thanks qi3ber