Parser error in some valid label names

[dansalvato]

In this code snippet:

ATKPARAM      MACRO
atk\<REPTN>_\1: rs.b       \2
              ENDM

The label name is valid, but the parser reports an error. When auto-formatting, the formatter inserts a colon after the underscore, which seems to indicate it thinks the label ends after the underscore but before the \1.

It seems any label name containing some characters, then a macro parameter, then an underscore, then another macro parameter, causes the parser error.

More tests/examples on label names:

something\1_\2 errors.

\1\1_\2 errors.

\1_\2 does not error.