Globals live in the package global symbol table. Lexical variables do not reside in the package global symbol table. They are held in a sort of internal pad. my variables (actually known as lexical variables) have their own private namespace, so to speak.

our is a kind of new-fangled way to declare package globals within a particular scope. It really has little effect unless you're using strict. But they're definately not the same thing as lexicals. You can't have two 'our $this' in the same package namespace and expect them to be different variables. They're the same variable.

Consider the following code:

{
    our $global = 10;    # Declare a package global.
    my $lexical = 10;    # Declare a block-scope lexical.
    {
        our $global = 20;    # Redeclare same package global.
        my $lexical = 20;    # Declare a new lexical in narrower scope
+.
    }
    # Narrower scope has ended.  Inner $lexical disappears.
    # $global remains.
    print "Global:  $global\nLexical: $lexical\n";
}
__OUTPUT__
Global:  20
Lexical: 10

[download]

Since there is only one symbol table per package, that package global declared with our is the same one throughout this script. But there can be as many different lexical variables of the same name as there are scopes to fit them in; each one is in its own namespace, which we (without XS) don't really have access to.

By the way, the variable declared by our $global is the same variable as $main::global, and $::global, and ${$::{global}} (assuming we're in package main). Each syntax has its own uses, but we don't usually see some of them in everyday code.


Dave

In reply to Re: Dumping symbol table shows variables declared with our but not my by davido
in thread Dumping symbol table shows variables declared with our but not my by Popcorn Dave

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