On linux I can do DISPLAY="" perl -d test.pl which will only use 1 xterm:

xterm:  DISPLAY is not set
######### Forked, but do not know how to create a new TTY. #########
  Since two debuggers fight for the same TTY, input is severely entang
+led.

  I know how to switch the output to a different window in xterms
  and OS/2 consoles only.  For a manual switch, put the name of the cr
+eated TTY
  in $DB::fork_TTY, or define a function DB::get_fork_TTY() returning 
+this.

  On UNIX-like systems one can get the name of a TTY for the given win
+dow
  by typing tty, and disconnect the shell from TTY by sleep 1000000.
[download]

I get mixed output/input from the different processes, though, so it's probably not very useful to run the program like this :-)