Unable to lookup array values using @index

When we are working with {{#each}}  helper we are facing following issue.

JSON: {arr1 : ["a","v"],arr2 : ["c","d"]}

Template:
{{#each arr1}}
{{../arr2.[0]}}
{{/each}}

Above code is  working fine. But when we use @index insteated of static index number in the arr2 its not working. we couldn't understand why @index value is not placed. 

For Example (Not working),

Template:1
{{#each arr1}}
{{../arr2.[@index]}}
{{/each}}

Template:2
{{#each arr1}}
{{../arr2.[index]}}
{{/each}}