Python's if __name__=="__main__" idiom for GNU Smalltalk?

Does such a thing exist?

Ruby:

if __FILE__ == $0
    main
end

Perl:

unless(caller) {
    main;
}

Lua:

if type(package.loaded[(...)]) ~= "userdata" then
    main(arg)
else
    module(..., package.seeall)
end