sub a_subroutine {
    my ($opt, @bad ) = @_;

    my $string          = delete $opt->{a_descriptively_named_string};
    my $desktop_info    = delete $opt->{desktop_config};
    my $important_files = delete $opt->(important_files} // [];

    checkopt( \%opt, \@bad,
        a_descriptively_named_string => defined $string,
        desktop_config               => ref $desktop_info eq 'HASH',
        important_files              => ref $important_files eq 'ARRAY',
   );

   # Do stuff.
}

# checkopt is a nice little function along these line.
# You can customize it a bit, (add support for testing for invocants, fancy crap with passing additional error messages, what have you)
# But in pretty much this form it has caught made many a bug shallow
sub checkopt {

    while (@_) {
        if ( ref eq 'HASH' ) {
            my $opts = shift;
           @args = keys @$opts;
            croak "Unexpected options in subroutine call: @args"
                if %$opts;
        }
        elsif ( ref eq 'ARRAY' ) {
            my $bad = shift;
            croak "Unexpected arguments in subroutine call."
                if @$bad

        }
        else {
            my $option_name = shift;
            my $option_okay  = shift;

            croak "Invalid option '$option_name' in subroutine call"
                unless $option_okay;
        }
    }

}