In response to your updated reply:

I noticed the same explanation in my docs, but that's for Perl 5.8. There is nothing mentioned in the 5.6 docs, as John noticed. I can't get the same behavior from 5.6:

open(F, '',   '/bin/ls',  '-l') || die $!;
open(F, '-|', '/bin/ls',  '-l') || die $!;  # works in 5.8
open(F, '|',  '/bin/ls',  '-l') || die $!;
open(F, '|',  '|/bin/ls', '-l') || die $!;
[download]

All of these die with "Can't use an undefined value as filehandle reference at ..." under 5.6.

If you're sure this behavior is the same in 5.6 and 5.8, just undocumented in 5.6, can you show examples of the correct modes to use?

blokhead