Hello all,

I wrote a module that has the single task of exporting all the symbols from one package up to its base package name.

E.g. Foo::Bar::Baz goes to just Baz and you can call Baz::quux().

This all works fine and I'm sure there's a module out there that already can do this but it's only a dozen lines of code or so. Anyway.

I'd like to be able to somehow cache what modules have already been exported so as to eliminate a lot of duplicate exports that happen.

I started with a poor man's memoization using a hash but no values ever get assigned to the hash since it's all executing at compile time (I guess).

I also tried inspecting the symbol table to see if the target package name (Baz) already had some CODE and skip it if so. The problem with that is a situation like this: "Foo::Bar qw(Baz)" and "Omg::Bbq qw(Baz)". Only one gets exported, the other dies when called.

So I call upon the wisdom of you, great monks, how to proceed.

Thanks, bmb

UPDATE: some code to illustrate the problem.

# Package/Exporter.pm
package Package::Exporter;
use strict;
use warnings;
use Carp qw[confess];
use Data::Dumper;


sub import {
    my( $class, @exports ) = @_;

    # turn 'Foo::Bar' into 'Foo/Bar'
    ( my $class_path = $class ) =~ s{::}{/}g;

    for my $export( @exports ) {
        no strict 'refs';

        # attempt to require 'Foo/Bar/Baz.pm'
        eval { require "$class_path/$export.pm"; };

        # die if there was an error
        if( $@ ) {
            confess __PACKAGE__ . "::import ${class}::import problem w
+ith $export - $@";
        }

# warn __PACKAGE__ . "::import ${class}::$export";
        # import, just in case
        "${class}::$export"->import;

        # loop through everything in 'Foo::Bar::Baz::'
        my @all_in_namespace = keys %{"${class}::${export}::"};

        # only the methods this time
        my @methods_in_namespace = grep { *{"${class}::${export}::${_}
+"}{CODE} } @all_in_namespace;

        for my $method( @methods_in_namespace ) {
            # and assign 'Baz::method' to 'Foo::Bar::Baz::method'
# warn sprintf( q["%s::%s" = sub () { "%s::%s::%s"}], $export, $method
+, $class, $export, $method );
            *{"${export}::${method}"}=\&{"${class}::${export}::${metho
+d}"};
        }
    }
}

1;

[download]
# Foo/Bar.pm
package Foo::Bar;
use strict;
use warnings;
use base 'Package::Exporter';

1;

[download]
# foo.pl
use Foo::Bar qw(Baz);

print Baz::quux(), "\n";

[download]
What I'd like to be able to do is somehow cache the fact that Foo::Bar::Baz was exported to Baz so the next time "use Foo::Bar qw(Baz);" is called, it skips the export.

In reply to Import singleton? by bennymack

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