m4: Quoted strings
3.2 Quoting input to 'm4'
=========================
A quoted string is a sequence of characters surrounded by quote strings,
defaulting to '`' and ''', where the nested begin and end quotes within
the string are balanced. The value of a string token is the text, with
one level of quotes stripped off. Thus
`'
=>
is the empty string, and double-quoting turns into single-quoting.
``quoted''
=>`quoted'
The quote characters can be changed at any time, using the builtin
macro 'changequote'. ⇒Changequote, for more information.