#!/usr/bin/perl --
use strict; use warnings;
use DateTime::Duration;
use DateTime::Format::Human::Duration;
use DateTime::Format::Natural;
@ARGV = ( "last week", "today" ) unless @ARGV;
my $dfn   = DateTime::Format::Natural->new;
my $start = $dfn->parse_datetime(shift);
my $end   = $dfn->parse_datetime(shift);
my $diff  = $end - $start;
print "$end - $start = ",
  DateTime::Format::Human::Duration->new->format_duration($diff), "\n";
__END__
2012-08-04T00:00:00 - 2012-07-28T00:00:00 = 1 week