use strict;
use warnings;

my $result =
{
  '10.4.20.21' => {          #IP Address from CPE equipment.
    '1' => '0x0a003edd8706', #Bridge table entry #1
    '2' => '0x1a003edd8706', #Bridge table entry #2
    '3' => '0xc03f0eddfb3b'  #Bridge table entry #3
  }
};

for my $mac (values %{(values %$result)[0]}) {
    print "Mac addr: $mac\n";
}