Your main problem is that the values of hashes can only be scalars, and not entire hashes. Lucky for you, a hash references (hashref) is also a scalar. You want to create your %args hash like this: my %args = (users => \%userHash, domains => \%domainHash, path => $path);

In your subroutine, you have to dereference the hashrefs in order to use them.

sub doSomethingUseful
{    
    my $args = shift;
   
    my $users = $args->{users};
    my $domains = $args->{domains};
    my $path = $args->{path};
 
    if (keys %$users > 1)
    {
        print("I was hoping you'd say that.");
    }
}
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