push @array, reverse @array[ 0 .. $n / 2 - 1 ];

##</code><code>##

qw(A B C D E)
qw(A B C D)
qw(A B C)
qw(A B)
qw(A)

##</code><code>##

A B C D E D C B A
A B C D D C B A
A B C B A
A B B A
A A

##</code><code>##

push @array, reverse @array[ EXPR ];