Beginning Web Development With Perl : From Novice to ... - Nabo

CHAPTER 1 ■ THE CGI MODULE 23You set the secure flag as another argument within the call to the cookie function, as inthis example:cookie(-name=>'cookiename',-value=>'cookievalue',-secure=>1);Note that if you don’t have an SSL-enabled web server, you won’t be able to test the secureflag.Environment VariablesEnvironment variables are values set by the environment where a process runs. In the case ofa CGI script, the environment variables are set by the web server on which they run. Thesevariables are automatically made available to your CGI script in the form of the %ENV hash.Viewing Environment VariablesThe script shown in Listing 1-12 makes it possible to view the environment variables availableto a CGI script on your web server.Listing 1-12. Viewing Environment Variables in a CGI Script#!/usr/bin/perl -Tuse strict;use CGI qw/:standard/;print header,start_html('Environment Variables');foreach my $variable (keys %ENV) {print p("$variable is $ENV{$variable}");}print end_html;exit;The only new items in this script are the three lines of the foreach loop, which is a standardPerl construct. Saving this script to your web server and accessing it through a browserwill result in a page similar to that in Figure 1-6.Some of the environment variables sent to your script by the web server are the result ofsettings on the server itself; others are sent from the server as read by the browser accessingthe script. One environment variable is HTTP_USER_AGENT. This environment variable is sometimesused (and misused) to determine the browser software and version accessing the page.Chapter 2 examines the use of HTTP_USER_AGENT to present a page based on the value of thevariable.