Autocomplete $foo[ for arrays and hashes.

[bscan]

When an array variable exists such as @foo = (3,4,5);, the variable can also be used as $foo[1]. Currently, the Navigator only autocompletes on @foo, but not $foo. Please add this form of autocomplete for both arrays and hashes, and include the opening left bracket (or brace). The relevant code is in completion.ts