Re^3: Defining a subroutine in another package

[Aristotle]

Ah so I can use them that way. Data::Dumper produces entries like 'UNIVERSAL::' => *{'::UNIVERSAL::'} for keys denoting a package name, which confused me - can you explain what that is? Is that a symbolic typeglob reference, or something completely different? (Incidentally, typeglobs are the only part of Perl I never even came close to grokking. I understand what they are supposed to be, but the concept is still very alien.)

Makeshifts last the longest.

[chromatic]

I think it's just there to look pretty. The leading package separator means it's in package main. The trailing package separator gets at the package stash. The typeglob dereference does point it at the typeglob. I'm not sure I'd call it symbolic, as a typeglob is sort of a special kind of hash...

All typeglobs do is associate the seven things that can be named with global names. Think of them as hashes that can only hold six keys -- SCALAR, ARRAY, HASH, CODE, IO, FORMAT. These are called slots, and you can get at the content of a glob by using the slot name as you would a hash key. The global (non-lexical) $foo, @foo, %foo, *foo, and &foo can all live within the typeglob *foo. Internally, anything that tries to use something with the name 'foo' will be resolved to use one of those things. Perl grabs the appropriate glob (resolving package names as necessary), then grabs the requested item from the appropriate glob slot.

Again, these are all things that have global and not lexical names.

You can copy typeglobs and assign to them. If you assign it a reference to something, it'll automatically populate (or overwrite) the appropriate slot. That's how Exporter works:

*{$package . '::mynewsub'} = \&mynewsub;