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

while (<DATA>)
{
   #one of many, many ways to get the 8 digit date
   my ($date) = /(\d{8}).*.log$/;
   print "$date\n";
}
=prints
20111031  // Oct 31, 2011
20110101  // Jan 01, 2011
=cut

__DATA__
AAAA*20111031*.log 
AAAA*sfdaf*20110101*.log