Doing things anonymously just brings alot of confusion, but it can be done. You can always get the widget's internal identifier with $widget->id;

#! /usr/bin/perl -w
use warnings;
use strict;
use Tk;

my $mw=MainWindow->new();

foreach(1..10)
    {
     my $e = $mw->Entry()->pack;
     $e->bind('<FocusIn>', sub { 
        print "@_\n"; 
        print "my entry is $_[0]\n";
            $_[0]->configure(-bg => 'hotpink');        
        } );     
        }
MainLoop;
[download]

but you are far better off storing everthing in hashes, because you can then get access to each entry from anywhere in the program.

#! /usr/bin/perl -w
use warnings;
use strict;
use Tk;

my $mw=MainWindow->new();

my %entries;

foreach(1..10)
    {
     $entries{$_}{'widget'} = $mw->Entry()->pack;
         $entries{$_}{'widget'}->bind('<FocusIn>', sub { 
             $_[0]->configure(-bg => 'hotpink');        
                 });
        }

$mw->after(5000,sub{

      foreach(2,4,6,8){
         $entries{$_}{'widget'}->configure(-bg => 'hotpink');
        }
     
     });
MainLoop;
[download]