/usr/share/doc/m4/examples
Edit: /usr/share/doc/m4/examples/translit.m4 (265B)
# traceon(`translit')dnl
translit(`GNUs not Unix', `a-z')
translit(`GNUs not Unix', `a-z', `A-Z')
translit(`GNUs not Unix', `A-Z', `a-z')
translit(`GNUs not Unix', `A-Z')
translit(`a-z', `a-')
translit(`A-Z', `A-Z-', `-A-Z')
translit(`GNUs not Unix', `Z-A', `a-z')