An
article
about Psh by Gregor N. Purdy you will find in
issue 18 (Summer 2000)
of
The Perl Journal.
In this article the author describes his shell and
also compares it to eight other Perl shells like Larry Walls "
while (<>) { eval; print $@; } "simple shell, the perl debugger,
timtosh
etc.pp.
Probably a good first read about Perl shells.