CGI

GET

use DBI;

my $query = new CGI;
my $param_value = $query->param('param_name');

• If the parameter was not sent, the value retrieved is an empty string.

POST

use DBI;

my $query = new CGI;
my $param_value = $query->param('param_name');

• If the parameter was not sent, the value retrieved is an empty string.

Environment variables

my $url       = $ENV{'REQUEST_URI'};

my $base_url  = $ENV{'SCRIPT_NAME'};
my $url_query = $ENV{'QUERY_STRING'};

HTML forms

Text field

• If the field is empty, the value retrieved is an empty string.
  

Radio button

• If no item was selected, the value retrieved is an empty string.
  

Check box

• If the field is unchecked, the value retrieved is an empty string.

Single-selection list

• If no item was selected, the value retrieved is an empty string.

Multiple-selection list

• The value is retrieved as an array of strings.
• If no items were selected, the value retrieved is an empty array.