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

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

##</code><code>##

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