my %HoA = (
    foo => [ 'bar', 'baz' ],
    qux => [ 'thud', 'xyz' ],
);
mysub(\%HoA); # pass a reference of the data structure

sub mysub {
    my $hash_ref = shift;
    # or if you want to directly work with a hash
    # instead of a reference inside the sub you can use
    # my %HoA = %{ shift };
    # Then you can do your stuff...
}