Shell Programming and Scripting

$ perl --version

This is perl, v5.8.8 built for i486-linux-gnu-thread-multi

Copyright 1987-2006, Larry Wall

Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on
this system using "man perl" or "perldoc perl".  If you have access to the
Internet, point your browser at http://www.perl.org/, the Perl Home Page.

$ perl test.pl --firstname John --surname Woo Wayne
firstname is set to  - John
surname is set to  - Woo Wayne

# cat /usr/perl5/5.8.4/lib/Getopt/Long.pm | more
# Getopt::Long.pm -- Universal options parsing

package Getopt::Long;

# RCS Status      : $Id: GetoptLong.pm,v 2.68 2003-09-23 15:24:53+02 jv Exp $
# Author          : Johan Vromans
# Created On      : Tue Sep 11 15:00:12 1990
# Last Modified By: Johan Vromans
# Last Modified On: Tue Sep 23 15:21:23 2003
# Update Count    : 1364
# Status          : Released

################ Copyright ################

# This program is Copyright 1990,2002 by Johan Vromans.
# This program is free software; you can redistribute it and/or
# modify it under the terms of the Perl Artistic License or the
# GNU General Public License as published by the Free Software
# Foundation; either version 2 of the License, or (at your option) any
# later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# If you do not have a copy of the GNU General Public License write to
# the Free Software Foundation, Inc., 675 Mass Ave, Cambridge,
# MA 02139, USA.

################ Module Preamble ################

use 5.004;

use strict;

use vars qw($VERSION);
$VERSION        =  2.34;

use lib '.'; # Include current directory

#!/usr/bin/perl

use strict;
use warnings;

print "I'm the main script\n";
Foo::Bar();
Foo->new()->Bar();
print "I'm the main script again\n";

package Foo;

sub Bar {
    my ($self) = @_;
    if ( ref $self eq "Foo" ) {
        print "I'm Foo->Bar()\n";
    }
    else {
        print "I'm Foo::Bar()\n";
    }
}

sub new {
    my ($class) = @_;
    my $self = {};
    bless( $self, $class );
    return $self;
}
1;

$ perl pkg.pl
I'm the main script
I'm Foo::Bar()
I'm Foo->Bar()
I'm the main script again