Perl module: Difference between revisions

Revision as of 21:04, 18 May 2009

Revision as of 07:45, 19 May 2009

Line 268:

==Perl packages and namespaces==

A running Perl program has a built-in namespace called "<code>main</code>", which is the default name. For example a subroutine called <code>Sub1</code> can be called as <code>Sub1()</code> or <code>main::Sub1()</code>. With a variable the appropriate sigil is placed in front of the namespace; so a scalar variable called <code>$var1</code> can also be referred to as <code>$main::var1</code>, or even <code>$::var1</code>. Other namespaces can be created at any time.

variable the appropriate sigil is placed in front of the namespace; so a scalar variable called $var1 can also be referred to as $main::var1, or even $::var1. Other namespaces

can be created at any time.

<source lang="perl">

package Namespace1;

$var1 = 1; # created in the Namespace1 namespace, which is also created if not pre-existing

our $var2 = 2; # also created in that namespace; our required if use strict is applied

my $var3 = 3; # lexically-scoped my-declared - NOT in any namespace, not even main - dynamically scoped

</source>

Line 283 ⟶ 279:

$Namespace2::$var1 = 10; # created in the Namespace2 namespace, which is also created if not pre-existing

our $Namespace2::var2 = 20; # also created in that namespace

my $Namespace2::var3 = 30; # compilation error, as dynamicallymy-scopeddeclared variablevariables canCAN'T't belong to a package

</source>