my %h;
for(qw/foo bar baz quux foo narf bar poit/) {
    $h{$_} = 1;
}

##</code><code>##

my (%h, @a);
for(qw/foo bar baz quux foo narf bar poit/) {
    push @a, $_ unless exists $h{$_};
    $h{$_} = 1;
}