CGI scripts

Constructing a CGI script using Perl is made enormously easier through use of the CGI module. This module can be used in a script as

use CGI qw(:common);

which imports into your script a whole range of routines useful in a CGI environment. The CGI.pm documentation contains a description of all the available routines, and you should consult this for details. Generally such routines fall into two classes:

• HTML shortcuts: Such routines are handy for generating common html constructions. For example, there is a routine h3('A level 3 heading') which will return the string <h3>A level 3 heading</h3> used to render a level 3 heading.
• parameter processing: These routines are used to check for values of available form elements, and retrieve those values if present. The main routine in this context is param(), used as my $sin = param('id'), which gets the value of the form element with name id and assigns it to the Perl variable $sin.

Here's a simple example taken from the CGI distribution of a script which asks you to fill in some values, and when the submit button is pressed, prints out to the screen the values entered. Note that the first line of the script,

#!C:/Perl/bin/perl

gives the location of the program to be used to run the script.

#!C:/Perl/bin/perl

use CGI ':standard';

print header;
print start_html('A Simple Example'),
    h1('A Simple Example'),
    start_form,
    "What's your name? ",textfield('name'),
    p,
    "What's the combination?",
    p,
    checkbox_group(-name=>'words',
		   -values=>['eenie','meenie','minie','moe'],
		   -defaults=>['eenie','minie']),
    p,
    "What's your favorite color? ",
    popup_menu(-name=>'color',
	       -values=>['red','green','blue','chartreuse']),
    p,
    submit,
    end_form,
    hr;

if (param()) {
    print 
	"Your name is: ",em(param('name')),
	p,
	"The keywords are: ",em(join(", ",param('words'))),
	p,
	"Your favorite color is: ",em(param('color')),
	hr;
}
print a({href=>'../cgi_docs.html'},'Go to the documentation');
print end_html;

To run this program, save it as, for example, tryme.cgi under the directory specified with the ScriptAlias directive in the httpd.conf file, and then go to http://localhost/cgi-bin/tryme.cgi.