Yet another variant:

my @elems = qw(a b c d e);

my $n = $#elems;
for my $elem (@elems) {
    print "last elem = $elem\n" if !$n--;
}
[download]

Update: as to your updated question: if you want to avoid creating a named array at any price, you could do something like this (but I'm not sure if I should seriously recommend that...)

my $n;
for my $elem (map {$n++; $_} qw(a b c d e)) {
    print "last elem = $elem\n" if !--$n;
}
[download]