Greenspun's Tenth Rule[0]

Any sufficiently complicated C or Fortran program contains an ad-hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp. - Philip Greenspun

[0] https://en.wikipedia.org/wiki/Greenspun%27s_tenth_rule

How would you subvert Greenspun in large codebases without Common Lisp? I once used Drools the rules engine which used a dynamic scripting language on Java objects. Python could have replaced that language, with much better tooling, errors etc.

Could you have written that system in a mix of Java and or another scripting language such as JRuby[0]?

[0] http://wiki.c2.com/?AlternateHardAndSoftLayers

IIRC MVEL language was integrated deeply into Drools. JRuby would have been awesome.