Programming Perl, 4th Edition

attributes

sub afunc : method;
my $closure = sub : method { ... };

use attributes;
@attrlist = attributes::get(\&afunc);

The attributes pragma has two purposes. The first is to provide an internal mechanism for declaring attribute lists, which are optional properties associated with subroutine declarations and (someday soon) variable declarations. (Since it’s an internal mechanism, you don’t generally use this pragma directly.) The second purpose is to provide a way to retrieve those attribute lists at runtime using the attributes::get function call. In this capacity, attributes is just a standard module, not a pragma.

Only a few built-in attributes are currently handled by Perl. Package-specific attributes are allowed by an experimental extension mechanism described in the section “Package-specific Attribute Handling” of the attributes(3) manpage.

Attribute setting occurs at compile time; attempting to set an unrecognized attribute is a compilation error. (The error is trappable by eval, but it still stops the compilation within that eval block.)

Only three built-in attributes for subroutines are currently implemented: locked, method, and lvalue. See Chapter 7 for further discussion of these. There are currently no built-in attributes for variables as there are for subroutines, but we can think of several we might like, such as constant.

The attributes pragma provides two subroutines for general use. They may be imported if you ask for them.

get

This function returns a (possibly empty) ...