Opens a pair of connected pipes like the corresponding system call. Note that if you set up a loop of piped processes, deadlock can occur unless you are very careful. In addition, note that Perl's pipes use IO buffering, so you may need to set
$| to flush your WRITEHANDLE after each command, depending on the application.
On systems that support a close-on-exec flag on files, that flag is set on all newly opened file descriptors whose
filenos are higher than the current value of $^F (by default 2 for
STDERR). See "$^F" in perlvar.