Where did you get that funny piece of code from?

Without context, it's hard to guess why it was written that way.

open(P, "|-") does an implicit fork. If that fails, its mostly due to hitting some limit (user limit or process table full). If the process limit is hit, the only way to execute another process is via exec - it substitutes the current process with the new process. exec never returns (since perl is gone if exec succeeds). If the exec fails, the code snippet exits 9 - let's take a guess at that number:

qwurx [shmem] ~> perl -le 'print "$_: ",$! = $_ for 8..10'
8: Exec format error
9: Bad file descriptor
10: No child processes
[download]

So, this code

• forks and opens a pipe to the child
• if that fails, it dups STDOUT and STDERR without checking if the open succeeds - why?
• it execs, and failing that, it's assumed that the filehandle dups didn't work?

Tss...

• what is in @cmd?
• the close($err); should be close($err) or warn "close: $!\n" - what happens if you run it like this?

I'd ask the author to explain what he meant to do, and that done, rewrite.

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}