CGI Developing

1. Here's one way to do it:

   use strict; use CGI qw(:standard);
   print header(), start_html("Add Me");
   print h1("Add Me"); if(param()) {
    my $n1 = param('field1'); my $n2 = param('field2'); my $n3 = $n2 + $n1;
   print p("$n1 + $n2 = <strong>$n3</strong>\n");
   }
   else {
    print hr(), start_form();
   print p("First Number:", textfield("field1"));
   print p("Second Number:", textfield("field2"));
   print p(submit("add"), reset("clear"));
   print end_form(), hr();
   }
   print end_html();
   

   If there's no input, simply generate a form with two textfields (using the textfield method). If there is input, we add the two fields together and print the result.

2. Here's one way to do it:

   use strict; use CGI qw(:standard);
   print header(), start_html("Browser Detective");
   print h1("Browser Detective"), hr(); my $browser = $ENV{'HTTP_USER_AGENT'};
    $_ = $browser; BROWSER:{ if (/msie/i) {
    msie($_);
   }
   elsif (/mozilla/i) {
    netscape($_);
   }
   elsif (/lynx/i) {
    lynx($_);
   }
   else {
    default($_);
   }
   } print end_html(); sub msie{ print p("Internet Explorer: @_. Good Choice\n");
   }
   sub netscape {
    print p("Netscape: @_. Good Choice\n");
   }
   sub lynx {
    print p("Lynx: @_. Shudder...");
   }
   sub default {
    print p("What the heck is a @_?");
   }
   

   The key here is checking the environment for the HTTP_USER_AGENT variable. Although this isn't implemented by every server, many of them do set it. This is a good way to generate content geared to the features of a particular browser. Note that we're just doing some basic string matching (case insensitive) to see what they're using (nothing too fancy).