#! perl -slw
use strict;

sub uniq { my %x; @x{@_} = (); keys %x }

my @array = ( 'A' .. 'Z', reverse 'A' .. 'Z' );

## Explicit sort block works as expected
print sort { $a cmp $b } uniq @array;

## implicit sort block "disables"!? the uniq() sub?
print sort uniq @array;

__DATA__
P:\test>junk
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZZYXWVUTSRQPONMLKJIHGFEDCBA