select current package
Major Section:  OTHER

(in-package "MY-PKG")

General Form:
(in-package str)
where str is a string that names an existing ACL2 package, i.e., one of the initial packages such as "KEYWORD" or "ACL2" or a package introduced with defpkg. For a complete list of the known packages created with defpkg, evaluate
(strip-cars (known-package-alist state)).
See defpkg. An ACL2 book (see books) must contain a single in-package form, which must be the first form in that book.