pipe RDRPARENT, WRTCHILD or die "Error: $!\n";
pipe RDRCHILD, WRTPARENT or die "Error: $!\n";
if (defined($pid=fork)) {
  if ($pid) {
    # In the parent
    # Close child's ends of the pipes
    close(WRTCHILD); close(RDRCHILD);
    # Continue, reading from RDRPARENT and writing to
    # WRTPARENT to communicate with the Java program.
  } else {
    # In the child
    # Close parent's ends of the pipe
    close(WRTPARENT); close(RDRPARENT);
    # Redirect STDOUT and STDIN to the pipes.
    open(STDOUT, ">&WRTCHILD") or die "Error: $!\n";
    open(STDIN, "<&RDRCHILD") or die "Error: $!\n";
    # Execute the java program
    exec("java prog.class");
    die "Exec error: $!\n";
  }
} else {
  die "Fork error: $!\n";
}