This snippet shows a subroutine which uses an original hack to compare two dates in dd.mm.yyyy format (can be easily ported to other formats).
#!/usr/local/bin/perl5 -w
# A little test code
print "hhh" if (Compare_Dates("25.11.1980", "23.12.1980") < 0);
# The sub. Observation: the integer formed by yyyymmdd
# can be compared numerically
sub Compare_Dates
{
my $date1 = $_[0];
my $date2 = $_[1];
$date1 =~ s/(\d{2})\.(\d{2})\.(\d{4})/$3$2$1/;
$date2 =~ s/(\d{2})\.(\d{2})\.(\d{4})/$3$2$1/;
return ($date1 - $date2);
}