What other kind of code (besides string eval) can generate methods on the fly?
AUTOLOAD is both a well known generator of methods/functions as a simulator. You might not find a
Foo->bar() method while searching the stash, but that doesn't mean you can't call 'bar' on Foo. AUTOLOAD may handle that; sometimes by installing a Foo::bar and then calling it or by just taking care of itself.
As for other ways beside string eval to generate methods, there's the assignment to the typeglob:
*{"Foo::bar"} = sub {print "Hello, world"};
or
*{"Foo::bar"} = \&{"Baz::quux"};
The latter is what typically happens at import time.