A safer method using Data::Diver:

use strict;
use Data::Diver 'DiveVal';
use Data::Dump 'dd';

my $root= {
    top => [
        {   first => 1 },
        {   second => {
                key => [
                    0, 1, 2, {
                        three => {
                            exists => 'yes',
                        },
                    },
                ],
            },
        },
    ],
};

DiveVal($root, qw/top 1 second key 3 three exists/) = 'no';
dd($root);
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Output:

{
  top => [
           { first => 1 },
           { second => { key => [0, 1, 2, { three => { exists => "no" 
+} }] } },
         ],
}
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