ikegami and Tanktalus have already shown you examples of better ways to do it, but in the spirit of TIMTOWTDI here are a couple other (ab)uses of the Getopt::Long features. The first takes advantage of the ability to assign a user-defined subroutine to an option to use during processing (which I use to set a flag and then store the value of the option). The second creates a copy of the original command line before it is processed and simply uses a regex to determine if a given option was present (without attempting to retrieve the value). I used a combination of single- and double-dashes to show it works both ways.

use strict;
use warnings;
use Getopt::Long;

# make a copy of the cmd line before GetOptions processes it
my $cmd_line = join( ' ', @ARGV );

my $saw_something = 0;
my @things;

GetOptions( 'something:s' => sub { shift @_; $saw_something = 1;
                                   push( @things, grep { $_ ne '' } @_
+ ); } );

if( $cmd_line =~ m/-?-something\b/ )
{
    print "I saw something on the cmd line\n";
}

if( $saw_something )
{
    if( scalar @things )
    {
        print 'And it was ' . join( ' ', @things ) . "\n";
    }
    else
    {
        print "But I don't know what I saw\n";
    }
}
[download]

For example:

C:\>test.pl --something NodeReaper
I saw something on the cmd line
And it was NodeReaper
[download]

There are times, however, when we know we saw something but we don't want to know what it was:

C:\>test.pl --something
I saw something on the cmd line
But I don't know what I saw
[download]

This works for multiple values, too:

C:\>test.pl --something a -something grue
I saw something on the cmd line
And it was a grue
[download]