[%- FOR i IN [0,1,2,3] -%]
    [%- i -%]:[%-loop.prev%]:[%-loop.next%]
[% END -%]
[%- FOR i IN {a => 0, b => 1, c => 3, d => 4 } -%]
    [%- i -%]:[%-loop.prev%]:[%-loop.next%]
[% END -%]