#!/bin/perl -w;
use strict;
foreach my $file (glob( "files/*")) # put the files dir here
  { rename( $file, correct( $file)) 
      or die "could not rename $file into " . correct( $file) . ": $!";
  }
sub correct 
  { my $date= shift; 
    my ($month, $year)= $date=~ /^(\d\d)(\d\d)/; 
    if( $year > 50) { $year +=1900} 
    else { $year+=2000}; 
    return $year.$month;
  }           

##</code><code>##

my @sorted_filenames= map  { $_->[0] }
                            sort { $a->[1] cmp $b->[1] }
                            map  { [$_, correct($_)] } 
                            glob( "files/*");