The package provides a macro \Inline that precedes a \def or
\gdef. Within the definition text of an inlined definition,
keywords such as \Expand may be used to selectively inline
certain expansions at definition-time. This eases the process
of redefining macros in terms of the original definition, as
well as definitions in which the token that must be expanded is
deep within, where \expandafter would be difficult and \edef is
not suitable. Another application is as an easier version of
\aftergroup, by defining a macro in terms of expanded local
variables, then ending the group with
\expandafter\endgroup\macro.

Homepage:
https://ctan.org/pkg/inlinedef
