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Re: [vox-tech] howto: perl modules and global variables
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Re: [vox-tech] howto: perl modules and global variables



On Thu, Jun 14, 2001 at 08:56:30AM -0700, Peter Jay Salzman wrote:
> i'm trying to figure out how a perl module accesses a global variable.
> below i show listings for the module (Hello.pm) and the program
> (testmodule.pl).  testmodule defines a global variable which i'd like
> to know how to access from within Hello.pm.
> 
> anyone know how to do this?

Your code almost works; see below for my coments.

> Hello.pm:
> 
>        package Hello;
>        require Exporter;          # } These set up an import
>        @ISA = qw(Exporter);       # } method, called implicitly
>        @EXPORT = qw( say_hello ); # } by use().
>        
>        sub say_hello {
>           print "Hello, world!\n";
>           print $globalvariable . "\n";

$globalvariable is uninitialized but is a ``global''.[1]

>        }
>        return 1;
> 
> 
> 
> testmodule.pl:
> 
>       #!/usr/bin/perl -w
>       use diagnostics;
>       use Hello;
>       
>       my $globalvariable = "hello world";

This $globalvariable is NOT a global. It is a lexical. The $globalvariable
referenced earlier is quite seperate. 

>       print "using scope specifier:\n";
>       Hello::say_hello();
>       
>       print "now without scope specifier:\n";
>       say_hello();
> 

[1] Quotes around global because perl does not really have globals per se.
All variables are associated with some namespace. Variables in the default
namespace mail can be treated as globals in most cases.

-- 
Henry House
OpenPGP key available from http://romana.hajhouse.org/hajhouse.asc


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