use strict;
use warnings;

my @month_name = qw(
    January February March April May June July August September
    October November December
    );
    
for my $startMonthIdx (0 .. 11) {
    my @sel = @month_name[$startMonthIdx .. 11, 0 .. $startMonthIdx - 1];

    print "$startMonthIdx: @sel\n";
}