examples/file.m4 - m4 - Git at Google

 changequote([[,]])dnl
 define([[quoteall]], [[patsubst([[[[$*]]]], [[,[ 	]+]], [[,]])]])dnl
 define([[group]], quoteall(include([[/etc/group]])))dnl
 dnl
 group()dnl
	changequote([[,]])dnl
	define([[quoteall]], [[patsubst([[[[$*]]]], [[,[ ]+]], [[,]])]])dnl
	define([[group]], quoteall(include([[/etc/group]])))dnl
	dnl
	group()dnl