$ perl -Mstrict -wle '
> my @arr = qw{ q w e r t y u i o p };
> my $sc  = sub { my( $a, $b ) = @_; $a cmp $b };
> my $rev = 0;
> my @asc = sort { $rev ? $sc->( $b, $a ) : $sc->( $a, $b) } @arr;
> $rev    = 1; 
> my @des = sort { $rev ? $sc->( $b, $a ) : $sc->( $a, $b) } @arr;
> print qq{@arr\n@asc\n@des};'
q w e r t y u i o p
e i o p q r t u w y
y w u t r q p o i e
$