#!/usr/bin/perl -w

# revdate.pl - by dual
#
# Usage: perl revdate.pl <dir>
#
# Reverses MMDDYY dates in file
# names to ISO 8601 YYYYMMDD

use strict;
use File::Find;

# Get directory or provide assistance
print "Usage: perl revdate.pl <dir>\n" and exit
  unless defined(my $dir = shift);

# Call reverse for each file
find(\&reverse, $dir);

# Reverse date here
sub reverse {
  # Skip directories
  if ( !(-d) ) {
    if ( $_ =~ /(.*)(\d{6})(.*)/ ) {
      # od = old_date
      my @od = split(//, $2);
      my $new_date = "20$od[4]$od[5]$od[0]$od[1]$od[2]$od[3]";
      rename $_, "$1$new_date$3";
    }
  }
}