Perl Syntax characters "::"

Question

I can't find anywhere what the :: is for in Perl. Example:

$someVariable::QUERY{'someString'};

Thanks!

Answer 1

These are package separators. I suspect the actual code is more like $SomePackage::SomeHash{'SomeKey'}. This syntax allows accessing a "package variable", in this case a hash, from some other package, or by its fully qualified name. You are probably more accustomed to seeing something like:

package SomePackage; 
our %SomeHash; 
$SomeHash{'SomeKey'} # do something with $SomePackage::SomeHash{'SomeKey'} here

A use case is setting up some module, like say Data::Dumper, which uses these package variables to control output:

use Data::Dumper;
local $Data::Dumper::Sortkeys = 1;
print Dumper { c => 3, a => 1, b => 2 };

... though this type of usage is typically avoided by using Object Oriented style.

See also: the famous "Coping with Scoping" article by MJD: http://perl.plover.com/FAQs/Namespaces.html