Under strict, global variables must contain the package name, eg: 
# CGI post max
$CGI::POST_MAX = 4096;

# if you are using strict, the global
# variable age in your 'main' script
# would need to be like this
$main::age = 31;

# or (same) with implicit namespace of 'main'
$::age = 31;

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If the package correctly exports variables/subs, they will be available in the namespace you are in. In the case of the CGI module, you can choose which elements are exported, eg 
use CGI qw/:standard/;

print header(),
      start_html(),
      h3('hello'),
      end_html();

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Take a look at the module for examples of other possible values.

Using 'my' to declare variables is best practice where possible. If you really do need truely global vars, then define by prepending "namespace::".

If you are not using strict, just defining a variable implies that the variable is global, ie: 

# no strict, so..
$age = 31

# is the same as these (in the 'main' script):
$::age = 31
$main::age = 31

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If you look, you will see that CGI.pm is NOT using 'strict', so it can define global variables such as $POST_MAX that are global, without having to explicitly using the package name.

But because these are global, you can access them from other packages through the namespace, eg: 

$CGI::NPH=1

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Still not very clear, is it? :) Why not create some play packages to experiment until this all sinks in?

Just my morning .02

cLive ;-)

Update: - please read tilly's comments below as well for info on stuff I didn't know about (our & vars - I still use Camel V2...). Also, added 'of main' to 'implicit namespace in code to avoid (possible) confusion. (All I meant was that $main:: and $:: are equivalent, with the main being implied in the $:: case. Not as Tilly thought, that $:: implies the current package.

In reply to Re: About packages and scopes by cLive ;-)
in thread About packages and scopes by nlafferty

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