my %g = ( Chicago=>{ Detroit=>250,
                     Cleveland=>400,
                     Denver=>2500,
                     SF=>4000 },
          Cleveland=>{ Chicago=>400,
                       NYC=>2500 },
          Detroit=>{ Chicago=>250,
                     Cleveland=>200 },
          NYC=>{ Cleveland=>2500,
                 SF=>7500 },
          SF=>{ NYC=>6500,
                Denver=>1500 },
          Denver=>{ SF=>1500,
                    Chicago=>2500 }
        );

d( \%g, 'Detroit', 'Cleveland'); # should be ( 'Detroit', 'Cleveland' )
d( \%g, 'Cleveland', 'Detroit' ); # should be 
( 'Cleveland', 'Chicago', 'Detroit' )
d( \%g, 'NYC', 'SF' ); # should be 
( 'NYC', 'Cleveland', 'Chicago', 'SF' ) OR ( 'NYC', 'Cleveland', 'Chicago', 'Denver', 'SF' )
d( \%g, 'SF', 'NYC' ); # should be ( 'SF', 'NYC' )
d( \%g, 'Denver', 'Cleveland' ); # should be ( 'Denver', 'Chicago', 'Cleveland' )
d( \%g, 'Cleveland', 'Denver' ); # should be 
( 'Cleveland', 'Chicago', 'Denver' );