where to use "use" and package

smackdab has asked for the wisdom of the Perl Monks concerning the following question:

In my Debug.pm file, it make a difference whether I put the "use" statements before or after the package declaration...

If I put them as this, I get undefined subroutine:

use File::Copy qw(copy);
use IO::File;

package Mods::Debug;
  [...stuff...]
    copy($file1, $file2);
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I can either move the "use" statements after the package declaration or I can explicitely call copy with File::Copy::copy(...)

But "copy()" has been @EXPORTed in the module...so I am confused ;-)

What is best? THANKS!
OFFTOPIC, but maybe a moderator is interested: If you use my title and then do a preview, the resulting title is only "where to use", the rest is chopped off

Comment on where to use "use" and package Download Code

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Re: where to use "use" and package by elusion (Curate) on Aug 01, 2002 at 03:31 UTC
The reason that you need to use the fully qualified name (`File::Copy::copy(...)`) is because by putting your use's before your package declaration, you've declared them into your main namespace. Any time you're in a file and haven't declared the namespace with package, the namespace defaults to main. After your package declaration, you're in the Mods::Debug namespace. So by putting the use's after the package declaration, you import them into the Mods::Debug namespace instead of main. This is the right way to do it. elusion : http://matt.diephouse.com	[reply] [d/l]
Re: where to use "use" and package by Abigail-II (Bishop) on Aug 01, 2002 at 09:29 UTC
Case matters. The default package is called `main`, not `Main`. Abigail	[reply] [d/l] [select]
Re: Re: where to use "use" and package by smackdab (Pilgrim) on Aug 01, 2002 at 05:20 UTC
Thanks, I didn't realize that each namespace would have to load in the somewhat "standard" modules. thanks !!!	[reply]
Re: Re: Re: where to use "use" and package by hossman (Prior) on Aug 01, 2002 at 07:08 UTC
If the methods in a module were really standard, they wouldn't be in that module -- they'd be builtins	[reply]
Re: where to use "use" and package by BrowserUk (Patriarch) on Aug 01, 2002 at 03:45 UTC
As I understand it, when your script is being compiled, the default package (read symbol table?) is `main::` until a package statement is processed, at which point a new (default) symbol table is set up. As the scoping of symbols in imported (`use`'d) modules is defined by the current default symbol table. Anything `use`'d before the first package will be aliased in `main::`, so after the `package Mods::Debug` statement, you could equally refer to `copy()` as `main::copy()` or `File::Copy::copy()`. The upshot: If you want to use symbols in a package, `use` them in the `package` where you want to use them:). Update:Corrected a couple of typoes. s/Main/main/ and s/File::copy()/File::Copy::copy()/.	[reply] [d/l] [select]
Re: where to use "use" and package by thunders (Priest) on Aug 01, 2002 at 15:23 UTC
placing a package in the same file as your main program is not really different than defining the package in another file. Had you put the package in a separate file it would be obvious why you couldn't copy, because you never imported the copy method from File::Copy.	[reply]