I would strongly recommend only accepting one form. If you want to accept both, have 2 different functions. That way if you ever want to add a third argument or fourth argument (such as, oh, a machine to connect to, a port, options for an SSH tunnel, etc) you'll be in good shape.

If you disregard said advice, you could do it as follows:

sub ssh_connect {
    my ($self, $user, $pass) = @_;
    if (3 < @_) {
        (undef, my %args) = @_;
        $user = $args{user} or confess("No user");
        $pass = $args{pass} or confess("No pass");
    }

    print "$user and $pass\n";
}
[download]

Alternately you could make the two forms be

$foo->ssh_connect($user, $password);
$foo->ssh_connect({user => $user, pass => $password});
[download]

and dispatch on whether there are fewer than 3 arguments. This is actually a saner way to go, but it does require {}.