I want to accept a filehandle given in the use line of my module:

use My::Module $fh;

This seems straightforward enough:

package My::Module;

our $fh;

sub import {
    shift;              # throw away my own package name
    $fh   = shift;
    if ( not -w $fh )   # check to see it's a good filehandle
       { die 'Bad filehandle in use My::Module' };
}

sub later {
    print $fh 'Arbitrary text.';
}

1;
[download]

Should I allow for the possibility that caller may decide to supply the filehandle using another syntax? If so, what should I allow?

use My::Module STDOUT;
use My::Module *STDOUT;
use My::Module 'STDOUT';
--?

Updates:

2010-05-30

The code I've actually written works fine for:

use My::Module *STDOUT;

It works okay, too, for:

use My::Module $fh;

... but with that, there's a fundamental complication which I did not consider while hurrying off in the other direction: The use line executes as a BEGIN block so, even though caller may appear to open $fh before, he doesn't, unless he does so in a previous BEGIN block:

BEGIN {
    open $::fh, '>>', '/var/foo.log';
}
use My::Module $::fh;
[download]

... and of course there are other approaches caller might employ. None of this, strictly speaking, is my worry (as author of My::Module); I just have to deal with the passed-in argument.

This is probably lunacy:

use My::Module STDOUT;

... or at least I can hope that nobody will be go down that road.

Is it worthwhile to support:

use My::Module 'STDOUT';

or perhaps:

use My::Module '/var/foo.log';

... or is that just too much gingerbread? Do you have a preferred syntax you'd like to see implemented?

2010-05-30 (never trust the .0 release)

rm ',' per bart.

Marginally more legitimate example code per almut.

2010-05-31

Agree with tye that it's ugly to accept:

use My::Module "STDOUT";

... I never even considered it. I don't really want to accept either of:

use My::Module STDOUT;
use My::Module 'STDOUT';

I think I'll continue to support, because so commonly used:

use My::Module *STDOUT;

...but I'll add support for:

use My::Module \*STDOUT;

I see that almut has a good word for:

use My::Module '/var/foo.log';

This may be just a bent feeler gauge off from the paygrade of the basic module under consideration but the small project as a whole contemplates opening filenames passed in as literal strings.

ikegami speaks wisely that opening $fh in a BEGIN block before the use line is icky. There isn't really an alternative, this being a source filter -- not without way too much hackery on existing code. Again, a helper/wrapper module is intended for open and pass in one line. I'm going to escalate the priority of this.

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