I don't know. It works for me:

$ perl -e 'open ERROR, "perl -le\"print q/stdout/; print STDERR q/stde
+rr/\" 2>&1 1>/dev/null|"; while (<ERROR>) { print }'
stderr
[download]

Are you positive that the program is sending its errors to stderr?

-sauoq
"My two cents aren't worth a dime.";