Are you seriously going to argue the inputs are constant? If you really believe that, why did you post such stupid solutions? You should have suggested

use strict;
use warnings;

print
'{
    "mike": 20,
    "johndeo@test.com": "test"
}';
[download]

But no, the OP used variables for a reason. It's because they are variable. And because of that, your first solution is buggy.