$ perl  doubly_linked.pl
Current: 0      Previous:       Next: 1
Current: 1      Previous: 0     Next: 2
Current: 2      Previous: 1     Next: 3
Current: 3      Previous: 2     Next: 4
Current: 4      Previous: 3     Next: 5

Current: 0      Previous:       Next: 0.5
Current: 0.5    Previous: 0     Next: 0.7
Current: 0.7    Previous: 0.5   Next: 1
Current: 1      Previous: 0.7   Next: 2
Current: 2      Previous: 1     Next: 3
Current: 3      Previous: 2     Next: 4
Current: 4      Previous: 3     Next: 5