That's a feature of CGI - it's treating your post data as an ISINDEX script. Definitely not something you want to rely on:

#!/usr/local/bin/perl

use strict;
use warnings;

use CGI;
use Data::Dumper;

my $cgi = CGI->new(  '{
      "Image": {
          "Width":  800,
          "Height": 600,
          "Title":  "View from 15th Floor",
          "Thumbnail": {
              "Url":    "http://www.example.com/image/481989943",
              "Height": 125,
              "Width":  "100"
          },
          "IDs": [116, 943, 234, 38793]
        }
   }'
);

print Dumper( $cgi );


$cgi = CGI->new(  '{
      "Image": {
          "Width=":  800,
          "Height": 600,
          "Title":  "View from 15th Floor",
          "Thumbnail": {
              "Url":    "http://www.example.com/image/481989943",
              "Height": 125,
              "Width":  "100"
          },
          "IDs": [116, 943, 234, 38793]
        }
   }'
);

print Dumper( $cgi );
[download]

The first dump will show you the JSON data associated with the keyword param. The second dump will show you the hilarity that will ensue if there's an equal signs somewhere in your data.

Your best bet is to provide a cgi_get_query method that deals with the data how you want to deal with it (as outlined in the docs for CGI::Application).

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