GNU M4 CONSIDERED DANGEROUS
Some people find ‘m4’ to be fairly addictive. They first use ‘m4’ for simple problems, then take bigger and bigger challenges, learning how to write complex sets of ‘m4’ macros along the way. Once really addicted, users pursue writing of sophisticated ‘m4’ applications even to solve simple problems, devoting more time debugging their ‘m4’ scripts than doing real work. Beware that ‘m4’ may be dangerous for the health of compulsive programmers.