Perl find closest date in array - perl

Question

How do I get the closest date that is earlier than the input date or equal to from an array using an input date?
For example, my array would look like this.
#dates = ("200811","200905","200912","201005","201202");
and my input date is
$inputdate = "201003";
How do I get the closest date in the array which is "200912".
The format of the date is YEARMM.
Thanks

Answer 1

Sort the dates, select only the ones preceding the input date, take the last such one:
print ((grep $_ <= $inputdate, sort #dates)[-1]);

Answer 2

use List::Util qw( max );
my $date = max grep { $_ <= $inputdate } #dates;

Answer 3

The logic here is to go one year back and change month from January to December if the month is January, otherwise go back one month in the same year.
I don't code much in Perl, the code in PHP is:
(I'm putting it here to give you the logic. Coding it should be trivial)
$dates = array("200811","200905","200912","201005","201202");
$inputdate = "201003";
$date = $inputdate;
while ($found==0) {
if (in_array($date, $dates)) {
$found = 1;
echo "the date is " . $date;
}
if ($date%100==1) { // if it's january, we need to change to december of the previous year
$date = $date - 100 + 12;
}
else {
$date = $date - 1; //go one month back in the same year
}
}