{ no warnings 'redefine'; *foo = \&Interface1::foo; }
print foo();
{ no warnings 'redefine'; *foo = \&Interface2::foo; }
print foo();

##</code><code>##

sub use_from {
    no strict 'refs';
    no warnings 'redefine';
    my $package = shift;
    *{ $_ } = *{ "$package\::$_" }{CODE} for @_;
}

##</code><code>##

 
use_from('Interface1', 'foo', 'bar'); 
foo(); bar()

use_from('Interface2', 'foo', 'bar')
foo(); bar();