Hi,

You forgot to escape  {"request":{"service":"test"},"data":{"test_input":"%2B2"}}

This is an error  CGI->new( 'data={"request":{"service":"test"},"data":{"test_input":"%2B2"}}' );

You want this  CGI->new( 'data=%7B%22request%22%3A%7B%22service%22%3A%22test%22%7D%2C%22data%22%3A%7B%22test_input%22%3A%22%252B2%22%7D%7D')

You want this  CGI->new( { data => $actual_data, } )

Its like writing

my $query = CGI->new({});
$query->param( 'data', $actual_data  );
print $query->self_url;
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This is how query-string/form-data works

Now if you were to use HTTP POST/PUT/PATCH you could use raw json in the request ; they call that AJAX

{
    use LWP;
    my $req = HTTP::Request->new(
        POST => 'http://127.0.0.1:80/'
    );
    $req->content_type( 'application/json' );
#~     $req->header('X-File-Name' =>  'tiny.gif' );
    $req->content_length( length $actual_data );
    $req->content( $actual_data );
    print "\n", $req->as_string, "\n";
}
__END__
POST http://127.0.0.1:80/
Content-Length: 59
Content-Type: application/json

{"request":{"service":"test"},"data":{"test_input":"%2B2"}}
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And to get at this ajax request from a .cgi you'd use

use CGI 4.35;
my $raw_data = CGI->new->param('POSTDATA'); # or PUTDATA or PATCHDATA
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An "fundvanced" example Mojolicious::Lite +and jQuery +AJAX + Mojo::Template