Yes. See I Don't Like Mondays. But if you want the first day of the month that doesn't have to be Monday, then it's not too hard with Time::Piece:

sub last_day {
   my $t = localtime;
   $t += Time::Piece::ONE_DAY * ($t->month_last_day - $t->mday + 1);
   return $t->fullday;
}
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jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)