=head3 C<xterm_get_fork_TTY>

This function provides the C<get_fork_TTY> function for X windows. If a
program running under the debugger forks, a new <xterm> window is opened and
the subsidiary debugger is directed there.

The C<open()> call is of particular note here. We have the new C<xterm>
we're spawning route file number 3 to STDOUT, and then execute the C<tty>
command (which prints the device name of the TTY we'll want to use for input
and output to STDOUT, then C<sleep> for a very long time, routing this output
to file number 3. This way we can simply read from the <XT> filehandle (which
is STDOUT from the I<commands> we ran) to get the TTY we want to use.

Only works if C<xterm> is in your path and C<$ENV{DISPLAY}>, etc. are
properly set up.

=cut

sub xterm_get_fork_TTY {
    ( my $name = $0 ) =~ s,^.*[/\\],,s;
    open XT,
qq[3>&1 xterm -title "Daughter Perl debugger $pids $name" -e sh -c 'tty 1>&3;\
 sleep 10000000' |];

    # Get the output from 'tty' and clean it up a little.
    my $tty = <XT>;
    chomp $tty;