You could use something like this:

my @a1 = qw(one two three);
my @a2 = qw(one five four);
my %h = map { $_ => 1 } (@a1, @a2);
my @r = keys(%h);
print "@r\n";
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This uses the map operator to create a hash, and then we extract the keys from this hash to an array.
There are no doubt other ways to do this - but this one's fairly straightforward.

Michael