B.4 Modules

12. The package keyword starts a new namespace (which lasts until another package declaration or until end of block). All user-defined global identifiers (variables, subroutines, filehandles) belong to this package. Lexical variables do not belong to any package.

    package Employee; # Put in file Employee.pm @employees = ("John", "Fred", "Mary", "Sue"); sub list_employee { print @employees; } 1;                # Last executing statement in file must be                    # non-zero, to indicate successful loading

13. To load module Employee:

    use Employee; #or  require Employee;

    Specify the load path with the -I command-line option, PERL5LIB environment variable, or @INC .

14. Access foreign package's variables and subroutines with fully qualified names:

    print @Employee::employees;     Employee::print();   

    Privacy is not enforced.

15. If a subroutine is not found in that package, a default subroutine AUTOLOAD() is called, if present. $AUTOLOAD is set to the fully qualified name of the missing subroutine.

16. To inherit module C from modules A and B, prime C's @ISA array with the names of its superclass modules:

    package A; sub foo{ print "A::foo called \n";} package C; @ISA = ("A", "B"); C->foo();               # Calls A::foo, because B does not