What does *{"$callpkg\::$_"} = \&{"$pkg\::$_"} mean and how do I fix it?

[Siegfried Heintze]

I have the following line of code:

my $id = async { &PopulateIndustryCompanyJobs($sIndustryName, $nThread);
$qCompleted->enqueue($sIndustryName); }

 

It causes this error:

Prototype mismatch: sub main::async (&;@) vs (&) at c:/Perl/lib/Exporter.pm
line 65.

Here is the line of source code from my ActiveState Perl distribution 5.8+:

  *{"$callpkg\::$_"} = \&{"$pkg\::$_"} foreach @_;

 

I have two questions:

(1) What the heck does that line of code do? We are assigning a reference of
a function in some package to a typeglob? What do all the {} do? What is the
\:: for? Why the quotes?

(2) Am I doing something wrong? My program seems to work. What should I
change?

 

Thanks again,

Siegfried

Below is the full code. Line 65 is nearly the last line of code.

----------------------------------------------------------------------------
----------------------------------------------

 

sub import {

  my $pkg = shift;

  my $callpkg = caller($ExportLevel);

 

  if ($pkg eq "Exporter" and @_ and $_[0] eq "import") {

    *{$callpkg."::import"} = \&import;

    return;

  }

 

  # We *need* to treat @{"$pkg\::EXPORT_FAIL"} since Carp uses it :-(

  my($exports, $fail) = ([EMAIL PROTECTED]"$pkg\::EXPORT"}, [EMAIL 
PROTECTED]"$pkg\::EXPORT_FAIL"});

  return export $pkg, $callpkg, @_

    if $Verbose or $Debug or @$fail > 1;

  my $export_cache = ($Cache{$pkg} ||= {});

  my $args = @_ or @_ = @$exports;

 

  local $_;

  if ($args and not %$export_cache) {

    s/^&//, $export_cache->{$_} = 1

      foreach (@$exports, @{"$pkg\::EXPORT_OK"});

  }

  my $heavy;

  # Try very hard not to use {} and hence have to  enter scope on the
foreach

  # We bomb out of the loop with last as soon as heavy is set.

  if ($args or $fail) {

    ($heavy = (/\W/ or $args and not exists $export_cache->{$_}

               or @$fail and $_ eq $fail->[0])) and last

                 foreach (@_);

  } else {

    ($heavy = /\W/) and last

      foreach (@_);

  }

  return export $pkg, $callpkg, ($args ? @_ : ()) if $heavy;

  local $SIG{__WARN__} = 

            sub {require Carp; &Carp::carp};

  # shortcut for the common case of no type character

  *{"$callpkg\::$_"} = \&{"$pkg\::$_"} foreach @_;

}