use feature ":5.14";
use warnings FATAL => qw(all);
use strict;
use Data::Dump qw(dump);

my @d = qw(26-04 26-04-12 26.04 26.04.12 30/8 30/08 30.08/12 1 12 aa aa/bb aa.c help);

say (/\A\d{2}[.-]\d{2}([.-]\d{2})?\Z/ ? "Matches for $_" : "FAILS for $_" ) for @d;