Instead of using a conditional, you could just store things in iteratively deeper hashes until you run out of elements in @data:

sub store_data {
    my( $root, $value, @key ) = @_;
    while( @key > 1 ) {
        $k = shift @key;
        $root->{ $k } ||= {};
        $root = $root->{ $k };
    };
    $root->{ $key[0] } = $value;
}

store_data( $devstats, $value, @data );
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Update: Code was missing a line