Agreed. The story does not look as favorable for XML::Simple anymore if the structure changes. If one makes it more robust using ForceArray => 1, then at least one more loop is required:

my $xml = XMLin( 'CC.xml', ( ForceArray => 1 ) );
for my $day (@{ $xml->{Week}[0]{Day} }) {
  next unless $day->{'day-of-week'} eq "Tuesday";
  for my $time ( @{ $day->{Times}[0]{Time} } ) {
    print $time->{'start-time'},"\n" if exists $time->{'start-time'};
  }
}
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Not really so "simple" anymore...