use Time::Local qw( timelocal_nocheck );
use POSIX       qw( strftime );

my ($sec,$min,$hour,$day,$mon,$year) = localtime;

for (0..3) {
   my $time = timelocal_nocheck($sec,$min,$hour,$day,$mon-$_,$year);
   print(strftime("%Y-%m", localtime($time)), "\n");
}