Getopt::Long.pm - Perl

It is interesting to note that the equality symbol (=) sign between the option name and the data type specifier tells Getopt::Long.pm that an option value *must* be provided for the option. Look what happens if, for example, you specify the "--age" option without a corresponding integer value:

$ ./script.pl --age
Option age requires an argument

In order to make an option value optional (try saying that fast!), use a colon (:) instead of an equality symbol (=), as below:


#!/usr/bin/perl
 
# import module
use Getopt::Long;
 
# read options
$result = GetOptions ("age:i" => $age);  
      

# print value
print "Input age is $age years";



Here, in the absence of a value for the option, Getopt::Long.pm will automatically assign 0 (for integer values) or an empty string (for string values) to the corresponding option variable. Take a look at the output of the script above to verify this:

$ ./script.pl --age
Input age is 0 years