Just found a possible bug -- when certain programs, such as ftp, are launched from yapsh, text from those is not displayed. Is this a bug in Shell.pm, or is it a bug in yapsh, or is it a bug in ActiveState 5.6 (which I'm using)?
Have you done any more work on this? I tried the "official" psh perl shell a while back but I'm curious how you are putting together a basic perl shell.