package Foo;
sub sort($&) {
   my ($self, $cmp) = @_;
   ...
   my @sorted = sort $cmp @list;    <-- sort compiled in one package
   ...
}

package Bar;
Foo->sort({ $a cmp $b });           <-- Sub compiled in another

##</code><code>##

package Foo;
sub sort($&) {
   my ($self, $cmp) = @_;
   ...
   my $caller = caller;
   my @sorted = eval("package $caller; sort \$cmp \@list");
   die $@ if $@;
   ...
}