use strict;
use warnings;
use Time::Piece;
use Test::More;

my $fmt     = '%d/%m/%Y';
my $date    = Time::Piece->strptime ('21/02/2013', $fmt);
my @within  = ('12/08/2013');
my @without = ('29/08/2013');
my $mon     = 6;

plan tests => @within + @without;

for my $other (@within) {
    ok (within_months ($mon, $date, Time::Piece->strptime ($other, $fmt)),
        "$other is within $mon months of $date");
}

for my $other (@without) {
    ok (! within_months ($mon, $date, Time::Piece->strptime ($other, $fmt)),
        "$other is not within $mon months of $date");
}

sub within_months {
    my ($mon, @d) = @_;
    if ($d[0] > $d[1]) { push @d, shift @d };
    my $start = $d[0]->add_months ($mon);
    return $start > $d[1];
}