When you get the results page, be sure to look at the page's URL in the browser's address bar.
In particular, notice the difference between the GET and POST method URL's.

Test printenv.pl (with "simple" query string).
Test printenv.pl (with "key-value" query string).

Test printenv.pl with GET method (with "key-value" query string).

1st input: 
2nd input: 
  

Test printenv.pl with POST method (with "key-value" query string).

1st input: 
2nd input: