(info "(make) Text Functions") says
'$(subst FROM,TO,TEXT)'
Performs a textual replacement on the text TEXT: each occurrence of
FROM is replaced by TO. The result is substituted for the function
call. For example,
$(subst ee,EE,feet on the street)
produces the value 'fEEt on the strEEt'.
OK, but also do mention how to deal with a FROM that has commas in it.
Or mention that there is no way to deal with it.
