AM_WITH_REGEX macro

[John Poltorak]

Apologies for this dumb question but I have difficulty understanding how 
the GNU Autotools work but reckon my understanding will improve with some 
pratical exercises. What I would like to do is to attempt to retrofit a 
check for '--with-regex' into an old version of diff. From what I have 
read this check is enabled by the use of regex.m4 by including 
AM_WITH_REGEX into configure.in. Would anything else be required?

I notice that this is an automake macro, but the rest are autoconf macros 
so would it be recognised by autoconf or do I need to run automake first?
There is no Makefile.am in this package. Do I need to create one?


-- 
John