#! /usr/bin/perl -w

use strict;
use Date::Calc qw/Days_in_Month/;

while( <DATA> ) {
    chomp;
    my( $year, $month ) = split;
    my $days = eval { Days_in_Month( $year, $month) };
    $days = 'who knows?' if $@;
    print "$year/$month => $days\n";
}
__DATA__
1996 1
1996 2
1998 2
2000 2
1900 2
1600 2
2001 2
2001 7
2001 12
2001 13
2001 0