my $pipe_qfn = 'xxx.fifo';

if (!-e $pipe_qfn) {
   system(mknod => $pipe_qfn, 'p')
      or die("Can't create pipe \"$pipe_qfn\": "
            .($?==-1 ? $! : "exit code $?")."\n");
}

open(my $pipe_fh, '>>', $pipe_qfn)
   or die("Unable to open pipe \"$pipe_qfn\": $!\n");

print $pipe_fh $msg;