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

12.2 Selecting What to Import

Fortunately, you can tell the
use operation to limit its actions. Do this by
specifying a list of subroutine names following the module name,
called the import list:

use File::Basename ("fileparse", "basename");

Now define the two given subroutines from the module, leaving your
own dirname alone. Of course, this is awkward to
type, so more often you'll see this written as:

use File::Basename qw( fileparse basename );

In fact, even if there's
only one item, you tend to write it with a qw( )
list for consistency and maintenance; often you'll
go back to say "give me another one from
here," and it's simpler if
it's already a qw( ) list.

You've protected the local
dirname routine, but what if you still want the
functionality provided by
File::Basename's
dirname? No problem. Just spell it out in full:

my $dirname = File::Basename::dirname($some_path);

The list of names following use
doesn't change which subroutine is defined in the
module's package (in this case,
File::Basename). You can always use the full name
regardless of the import list, as in:[4]

[4] You
don't need the ampersand in front of any of these
subroutine invocations because the subroutine name is already known
to the compiler following use.

my $basename = File::Basename::basename($some_path);

In an
extreme (but extremely useful) case, you can specify an empty list
for the import list, as in:

use File::Basename (  );              # no import
my $base = File::Basename::basename($some_path);

An empty list is different from an
absent list. An empty list says
"don't give me anything in my
current package," while an absent list says
"give me the defaults."[5] If the
module's author has done her job well, the default
will probably be exactly what you want.

[5] As you'll see later in this chapter, the
default list comes from the module's
@EXPORT array.