Extensible Shell
(es) A Unix shell written by Byron Rakitzis <byron@netapp.com> and Paul Haahr <haahr@adobe.com>, derived from rc. Es has real functions, closures, exceptions and lets you redefine most internal shell operations.
Version: 0.84.
ftp://ftp.sys.utoronto.ca/pub/es/.
["Es - A Shell with Higher Order Functions", P. Haahr et al, Proc Winter 1993 Usenix Technical Conference].