In this fourth slide, we introduce the CGI program processing the form.
Remember that the CGI protocole treats data input in the form as variable pairs:
field name, field value. The CGI library has a method, called param, which
provides, for each field name, the value entered by the user.
If for example, the user entered the value 25 in field named age, then the
statement:
if ($query->param('age') > 18)
will compare the value entered in the age field to 18, and return true or
false based on the result of the comparison.
1. THE CGI PROGRAM:
#!/usr/local/bin/perl
use CGI;
$query=new CGI;
print $query->header;
print "<html><head><title>Are you old enough to vote?</title></head>\n";
print "<body>";
if ($query->param('age') > 18)
{
print "<p>You are old enough to vote.<p>\n";
}
else
{
print "<p>You are not yet old enough to vote.<p>\n";
}
print "</body></html>";
2. PROGRAM DESCRIPTION:
The first four lines are identical as slide #2
The next two lines display the header and the body of the HTML form:
The next lines (7-14) check if we are old enough to vote and display the
relevant message.
Line 15 closes the body and html tags.
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