These are exactly the same after the compile stage

__PACKAGE__->hello('text1');
Foo->hello('text1');
[download]

These are also the same

hello(__PACKAGE__, 'text1');
hello('Foo', 'text1');
[download]

The difference between f('x') and 'x'->f() is that if there is no sub f {} in Foo @INC will be used to look for one.

Look at UNIVERSAL and perltoot.