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cgi.pl -- Read CGI parameters
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Below is a very simple CGI script that prints the passed parameters. To test it, compile this program using the command below, copy it to your cgi-bin directory (or make it otherwise known as a CGI-script) and try the query http://myhost.mydomain/cgi-bin/cgidemo?hello=world

% swipl -o cgidemo --goal=main --toplevel=halt -c cgidemo.pl
:- use_module(library(cgi)).

main :-
    set_stream(current_output, encoding(utf8)),
    format('Content-type: text/html; charset=UTF-8~n~n', []),
    format('<html>~n', []),
    format('<head>~n', []),
    format('<title>Simple SWI-Prolog CGI script</title>~n', []),
    format('</head>~n~n', []),
    format('<body>~n', []),
    format('<p>', []),
    format('</body>~n</html>~n', []).

print_args([A0|T]) :-
    A0 =.. [Name, Value],
    format('<b>~w</b>=<em>~w</em><br>~n', [Name, Value]),
Source cgi_get_form(-Form)
Decodes standard input and the environment variables to obtain a list of arguments passed to the CGI script. This predicate both deals with the CGI GET method as well as the POST method. If the data cannot be obtained, an existence_error exception is raised.
Form- is a list of Name(Value) terms.