$a[-1]  # last element
$a[-2]  # second-last element

##</code><code>##

@a[-2, -1]  # second-last and last element

##</code><code>##

>perl -E"@a = qw( a b c d e f ); say for @a[4..-1]"

>perl -E"@a = qw( a b c d e f ); say for @a[-3..-1]"
d
e
f

>perl -E"@a = qw( a b c d e f ); say for @a[-1..-3]"

>perl -E"@a = qw( a b c d e f ); say for @a[reverse -3..-1]"
f
e
d

>perl -E"@a = qw( a b c d e f ); say for reverse @a[-3..-1]"
f
e
d