JCL: /J-C-L/ N. 1. IBM's Supremely {rude} Job Control Language.

:JCL: /J-C-L/ n. 1. IBM's supremely {rude} Job Control
Language. JCL is the script language used to control the execution
of programs in IBM's batch systems. JCL has a very {fascist}
syntax, and some versions will, for example, {barf} if two
spaces appear where it expects one. Most programmers confronted
with JCL simply copy a working file (or card deck), changing the
file names. Someone who actually understands and generates unique
JCL is regarded with the mixed respect one gives to someone who
memorizes the phone book. It is reported that hackers at IBM
itself sometimes sing "Who's the breeder of the crud that mangles
you and me? I-B-M, J-C-L, M-o-u-s-e" to the tune of the
"Mickey Mouse Club" theme to express their opinion of the
beast. 2. A comparative for any very {rude} software that a
hacker is expected to use. "That's as bad as JCL." As with
{COBOL}, JCL is often used as an archetype of ugliness even by
those who haven't experienced it. See also {IBM}, {fear and
loathing}.
-- The AI Hackers Dictionary