> (which is a bit different than JSONP).

try reading JSONP and explain the difference. You might figure out how to use JSON then! (hint: + padding)

> Is the $perl_scalar my $testHASH in our case?

from JSON

$json_text = to_json($perl_scalar)

Converts the given Perl data structure to a json string.
[download]

If you try to understand JSON and Perl Data Structures you will see that they have the exactly same structure with little syntactic differences (enough to justify a module in that case)

I.o.w. $perl_scalar is a ref to a HoH or HoA or AoH (... and so on) reflecting the JSON structure you desire.

Please try ...

• to read the links I gave you,
• use search engines for example code
• generally try experimenting with code¹

... to improve your coding skills.

Hope this helped! :)

update

¹) use Data::Dumper or Data::Dump to inspect data structures