texlive-collectbox 51265 Collect and process macro arguments as boxes
The package provides macros to collect and process a macro argument (i.e., something which looks like a macro argument) as a horizontal box rather than as a real macro argument. The "arguments" are stored as if they had been saved by
\savebox or by the
lrbox environment. Grouping tokens
\egroup may be used, which allows the user to have the beginning and end of a group in different macro invocations, or to place them in the begin and end code of an environment. Arguments may contain verbatim material or other special use of characters. The macros were designed for use within other macros.