module Exporter;

##</code><code>##

use strict;
use warnings;
use warnings::register;    #assuming this continues to exist...

##</code><code>##

sub import($pkg : ARRAY $export=undef, ARRAY $ok=undef, HASH $tags=undef) {

##</code><code>##

ARRAY $export=undef

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ARRAY $export //= undef

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    my $from_pkg=caller.package;

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    my $from_pag = caller.MY.package;

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    pkg_alias($from_pkg, "Exporter::From");
    &Exporter::From::import := &myimport;

##</code><code>##

sub pkg_alias($original, $new) {
    #Any sufficiently encapsulated hack...
    no strict 'refs';

    %{"${original}::"} := %{"${new}::"};    #XXX will this actually work?
}

##</code><code>##

sub myimport($exp_from : *@symbols=() : *@options=()) {

##</code><code>##

    my $exp_to=caller.package;    #is this how caller is used?

    pkg_alias($exp_from, "Exporter::From");
    pkg_alias($exp_to, "Exporter::To");

    #defaults
    @symbols //= @Exporter::From::EXPORT;

##</code><code>##

	$foo ||= 'bar';

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    $foo //= $bar // $baz // 'nothing to see here, folks';

##</code><code>##

    #expand tags to their values
    @symbols=map {
        /^:/ ??
            @{%Exporter::From::EXPORT_TAGS}{$_}} ::
            $_
    } @symbols;

##</code><code>##

    for(@symbols) {
        #handle version numbers
        if(/^[\d.]+$/) {
            $exp_from.require_version($_);
            next;
        }

##</code><code>##

        #handle renamed exports
        my($to, $from)=$_.ref eq 'PAIR' ? ($_.left, $_.right) : ($_, $_);

##</code><code>##

        for($to, $from) {
            #make sure it has some sort of sigil
            $_='&' _ $_ unless m'^[$@%&]';
        }

##</code><code>##

        warnings::warnif("$from exported from $exp_from conflicts with existing $to at $(caller.file) line $(caller.line).\n")
            if defined %Exporter::To::{$to};

##</code><code>##

        %Exporter::To::{$to}=%Exporter::From::{$from};
    }

##</code><code>##

    for(@options) {
        my($sign, $name, $value)=/[+-]([[\w]&&[^\d]]\w+)(?:=(.*))?/s;
        my $targ := ${$Exporter::From::{$name}};

        given($sign) {
            when('+'): {
                if(defined $value) {
                    $targ=$value;
                }
                else {
                    $targ is true;
                }
            }

            when('-') {
                if($targ.props{true}) {
                    $targ is false;
                }
                else {
                    undef $targ;
                }
            }
        }
    }
}

##</code><code>##

    if(defined $export) {
        @Exporter::From::EXPORT=@$export;
    }

    if(defined $ok) {
        @Exporter::From::EXPORT_OK=@$ok;
    }

    if(defined $tags) {
        %Exporter::From::EXPORT_TAGS=%$tags;
    }
}

##</code><code>##

    if(defined $export) {
        @Exporter::From::EXPORT = $export;
    }

    if(defined $ok) {
        @Exporter::From::EXPORT_OK = $ok;
    }

    if(defined $tags) {
        %Exporter::From::EXPORT_TAGS = $tags;
    }
}