Here is something it get you started:

#!/usr/bin/perl -wT
use strict;
use POSIX qw(mktime);

my $oct7 = daysago(7,10,2001);

print "October 7th was $oct7 days ago\n";

sub daysago {
  my $day = shift;
  my $month = shift;
  my $year = shift;
  my $then = mktime((localtime)[0..2], $day, $month-1, $year-1900);
  my $delta = time - $then;

  return int($delta/60/60/24);
}

=OUTPUT
October 7th was 24 days ago
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-Blake