Info Catalog
m4: Comments
m4: Syntax
m4: Input processing
3.4 Other kinds of input tokens
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Any character, that is neither a part of a name, nor of a quoted string,
nor a comment, is a token by itself. When not in the context of macro
expansion, all of these tokens are just copied to output. However,
during macro expansion, whitespace characters (space, tab, newline,
formfeed, carriage return, vertical tab), parentheses ('(' and ')'),
comma (','), and dollar ('$') have additional roles, explained later.