phpman > perldoc > pipe(2)

    pipe READHANDLE,WRITEHANDLE
            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.

            Returns true on success.

            See IPC::Open2, IPC::Open3, and "Bidirectional Communication
            with Another Process" in perlipc for examples of such things.

            On systems that support a close-on-exec flag on files, that flag
            is set on all newly opened file descriptors whose "fileno"s are
            *higher* than the current value of $^F (by default 2 for
            "STDERR"). See "$^F" in perlvar.