Your key should be 'range(?)' — as the docs say:

"The results of named subrules are stored in the hash under each subrule's name (including the repetition specifier, if any)"

With that change, i.e.

     if (defined @{$item{'range(?)'}->[0]}) {
             my @arr = @{$item{'range(?)'}->[0]};
             foreach my $i (@arr) {
                     print $i."\n";
             }
     }
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I do get the expected output:

input
2
0
a
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