Apache::Reload module seems to apply the same technique. Here a snippet: 
        if ($mtime > $Stat{$file}) {
            delete $INC{$key};
 #           warn "Reloading $key\n";
            if (my $symref = $UndefFields{$key}) {
#                warn "undeffing fields\n";
                no strict 'refs';
                undef %{$symref};
            }
            require $key;
            warn("Apache::Reload: process $$ reloading $key\n")
                    if $DEBUG;
        }
        $Stat{$file} = $mtime;

[download]
The same technique, except that it copes with your "${package}::FIELDS" (which $symref in the snippet above is a reference to).

For further info about %FIELDS, you can check the fields pragma man page (but check 5.8.0 perldelta about the deprecation of 5.6.1 pseudohashes' "user visible" implementation).

Update: Clarified final note.

In reply to Re: Reloading changed modules by larsen
in thread Reloading changed modules by castaway

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