Some people find m4 to be fairly addictive. They first use m4 for simple problems, then take bigger and bigger [..] m4 macros along the way. Once really addicted, users pursue [..] sophisticated m4 applications even [..] more time [..] than doing real work. Beware that m4 may be dangerous for the health of compulsive programmers.
~ GNU M4 1.4.17 macro processor