sub sort_unique_hash {
    my %hash;
    @hash{@_} = ();
    return sort keys %hash;
}

##</code><code>##

Benchmark: timing 100000 iterations of foreach, hash...
foreach: 14 secs (13.50 usr  0.00 sys = 13.50 cpu)
hash:  6 secs ( 5.85 usr  0.00 sys =  5.85 cpu)

##</code><code>##

@list = qw/foo bar baz foo quack bar baz/;

##</code><code>##

@list = ('foo') x 1000;

##</code><code>##

Benchmark: timing 1000 iterations of foreach, hash...
foreach: 12 secs (11.82 usr  0.00 sys = 11.82 cpu)
hash:  1 secs ( 0.88 usr  0.00 sys =  0.88 cpu)