$ perl -e '
    my %seen;
    my @values = grep !$seen{$_}++, @ARGV;
    print "@values\n";
' 1 2 1 2 3 1 2 3
1 2 3

##</code><code>##

$ perl -E '
    local $, = " ";
    say grep {state $seen; !$seen->{$_}++} @ARGV;
' 1 2 1 2 3 1 2 3
1 2 3

##</code><code>##

$ perl -E 'say "@{[grep {state $seen; !$seen->{$_}++} @ARGV]}";' 1 2 1 2 3 1 2 3
1 2 3