This command begins the definition part.
‘@m’ defines an FWEB macro, and also marks the next identifier as defined here. It is equivalent to
‘@m’ == ‘@M@[’
(see Forward referencing).
For a detailed discussion of FWEB macros, see MACROS and PREPROCESSING.
The distinction between ‘@m’ and ‘@M’ is analagous to the distinction between ‘@a’ and ‘@A’. See ‘@a’: Begin code part of unnamed section, and mark.