Learning Perl Objects, References amp;amp; Modules [Electronic resources] نسخه متنی

12.8 Importing with Exporter

Earlier we skipped over that
"and now magic happens" part where
the import routine (defined by the module author)
is supposed to take File::Basename::fileparse and
somehow alias it into the caller's package so
it's callable as fileparse.

Perl provides a lot
of introspection capabilities. Specifically, you can look at the
symbol table (where all subroutines and most variables are named),
see what is defined, and alter those definitions. You saw a bit of
that back in the AUTOLOAD mechanism earlier. In
fact, as the author of File::Basename, if you
simply want to force filename,
basename, and fileparse from
the current package into the main package, you can
write import like this:

sub import {
no strict 'refs';
for (qw(filename basename fileparse)) {
*{"main::$_"} = \&$_;
}
}

Boy, is that cryptic! And limited. What if you
didn't want fileparse? What if
you invoked use in a package other than
main?

Thankfully, there's a standard
import that's available in the
Exporter module. As the module author, all you do
is add:

use Exporter;
our @ISA = qw(Exporter);

Now
the import call to the package will inherit upward
to the Exporter class, providing an
import routine that knows how to take a list of
subroutines[12] and export
them to the caller's package.

[12] And variables, although far less common,
and arguably the wrong thing to do.