# Import nothing -- fastest but requires additional coding
use Some::Module ();
...
Some::Module::some_function();
Some::Module::other_function();

# Import just the parts you intend to use -- still fast; less coding
use Some::Module qw{some_function other_function};
...
some_function();
other_function();

# Import everything -- could be very slow
use Some::Module;
...
any_function();