>> ... and gather stdout, stderr.

Quoting from perlop ...

qx/STRING/

...

To capture a command's STDERR and STDOUT together:

    $output = `cmd 2>&1`;
[download]

This works for me, on WinXP, as in the example below.
To generate output going to stdout in one case and to stderr in another case, my script calls a Perforce command (p4 change -o) with a good changelist (43026) - this writes to stdout, and then with an inexistent one (143026) - this writes to stderr.

#!/usr/bin/perl
use strict;
use warnings;

printf STDERR "1 stdout:   %s\n\n", ` p4 change -o 43026 `;
printf STDERR "2 stdout:   %s\n\n", ` p4 change -o 143026 `;
printf STDERR "3 stdout+stderr 2>&1:   %s\n\n", ` p4 change -o 143026 
+2>&1 `;

__END__


# typical output on my machine #

1 stdout:   # A Perforce Change Specification.


Change 143026 unknown.
2 stdout:   

3 stdout+stderr 2>&1:   Change 143026 unknown.
[download]

HTH
rudif