use Getopt::Long;

my $data   = "file.dat"; my $length = 24; my $verbose; GetOptions ("length=i" => \$length,    # numeric             "file=s"   => \$data,      # string             "verbose"  => \$verbose)   # flag or die("Error in command line arguments\n");    

DESCRIPTION

The Getopt::Long module implements an extended getopt function called GetOptions(). It parses the command line from @ARGV, recognizing and removing specified options and their possible values.

 

my $verbose = '';   # option variable with default value (false)

my $all = '';       # option variable with default value (false) GetOptions ('verbose' => \$verbose, 'all' => \$all);

The option name as specified to the GetOptions() function is called the option specification. Later we'll see that this specification can contain more than just the option name. The reference to the variable is called the option destination.
The call to GetOptions() parses the command line arguments that are present in @ARGV and sets the option variable to the value 1 if the option did occur on the command line. Otherwise, the option variable is not touched. Setting the option value to true is often called enabling the option.

GetOptions() will return a true value if the command line could be processed successfully. Otherwise, it will write error messages using die() and warn(), and return a false result.