conversion from SAS environment variable to library implicitly

It is interesting that a SAS environment variable can be used as a SAS library.
The library should be assigned implicitly.

*sample code;
options noxwait;
options set=test="c:\";
libname test clear; *de-assign the library;
libname test list; *the library appear again;

*In this way, we can define user-defined formats at SAS invocation;
-set fmtlib "format-path"
-fmtsearch (work fmtlib)