my $foo = Something.new();

##</code><code>##

sub foo($x, $y) { say $x ~ $y }
my $foo_ref = &foo;   # leaves $foo_ref writable
my $foo    := &foo;   # basically the same, but you can't
                      # assign to $foo afterwards

# passing values to a signature is a form of 
# binding too, so this works:
sub c(&func) {
  func(42, 23);
}
c(&foo);
c($foo);
c($foo_ref);