Wouldn't it be nicer to have the number you want to tack on to a name be an actual array index? This gives you an Array-of-Arrays in a compact way:

my @arr_new = map { # generate $something2add from $_
                    [$something2add];
                  } @arr_name;
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Now, $arr_new[7] is a reference to what your old @arr_new7 would have been.

After Compline,
Zaxo