Pushed the wrong button and added this to soon.
What I wanted to say is that you modify open_subprocess_connection so that it always generates the same series of pipe names (i.e. 1, 2, 3, 4) instead of the "random" name. Then run the test_redirection_master.rexx examle (which calls test_redirection.rexx). You will see that open_subprocess_connection fails.
I found this in 3.3, the...
2009-04-10 11:08:14 UTC in Regina REXX Interpreter