There is also the packSlaves method, but you won't know for sure which entry is which, although I would ASSUME they are listed in creation order.

#! /usr/bin/perl -w
use Tk;
$mw=MainWindow->new();
foreach(1..10)
    {
    $mw->Entry()->pack;
    }

$mw->after(100,sub{
      print $mw->packSlaves,"\n";
    });

MainLoop;
[download]

P.S. There is also the Tk::caller method, but it requires a bind.