Question

Some namespaces are long and annoying. Lets say that i downloaded hypothetical package called FooFoo-BarBar-BazBaz.tar.gz, and it has the following modules:

FooFoo::BarBar::BazBaz::Bill
FooFoo::BarBar::BazBaz::Bob
FooFoo::BarBar::BazBaz::Ben
FooFoo::BarBar::BazBaz::Bozo
FooFoo::BarBar::BazBaz::Brown
FooFoo::BarBar::BazBaz::Berkly
FooFoo::BarBar::BazBaz::Berkly::First
FooFoo::BarBar::BazBaz::Berkly::Second

Is there a module or technique I can use that’s similar to the C++ ‘using’ statement, i.e., is there a way I can do

using FooFoo::BarBar::BazBaz;

which would then let me do

my $obj = Brown->new();

ok $obj->isa('FooFoo::BarBar::BazBaz::Brown') ;  # true
# or...
ok $obj->isa('Brown'); # also true

Answer 1

The aliased pragma does this:

use aliased 'FooFoo::BarBar::BazBaz::Bill';

my $bill = Bill->new;

aliased is syntactic sugar for

use constant Bill => 'FooFoo::BarBar::BazBaz::Bill';
# or 
sub Bill () {'FooFoo::BarBar::BazBaz::Bill'}

The downside of this is that normal usage of package names as arguments is done with quoted strings:

$obj->isa('FooFoo::BarBar::BazBaz::Bill')

But the constant subroutine needs to be a bare word:

$obj->isa(Bill);

Which just seems like a bug waiting to happen.

Alternatively, you could just use Perl’s builtin support for namespace aliasing:

package Foo::Bar::Baz::Bill;

sub new {bless {}}

package Foo::Bar::Baz::Tom;

sub new {bless {}}

package main;

BEGIN {*FBB:: = *Foo::Bar::Baz::}  # the magic happens here

say FBB::Bill->new;  # Foo::Bar::Baz::Bill=HASH(0x80fd10)

say FBB::Tom->new;   # Foo::Bar::Baz::Tom=HASH(0xfd1080)

Regarding the ->isa('shortname') requirement, the aliased stash method works with quoted strings as usual:

my $obj = FBB::Bill->new;

say $obj->isa('FBB::Bill');           # prints 1
say $obj->isa('Foo::Bar::Baz::Bill'); # prints 1

The effect of a compile time alias BEGIN {*short:: = *long::package::name::} is global across all packages and scopes. This is fine as long as you pick an empty package to alias into.