It is no possible to have several one character quote strings or comment delimiters to change the format of macro calls to use active characters like in TeX and probably most useful to change what input characters are treated as letters when looking for macro calls. See the manual section for more details. Support for loadable modules. GNU m4 now has support for dynamic loading of compiled modules at runtime. A module can define any number of new build in macros which will be indistinguishable from the standard set of build in macros.
Modules can also override existing build in macros.
Better control of sync-lines generation. The new build in macro 'syncoutput' allows better control of the generation of sync-lines. They can now be turned on or off at will.