my $parent = 'xxx xxx xxx';
my $count = my @items = split(/ /, $parent);
print "$count\n";  # 3
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Since you have a count, all you need to check if there are duplicates is check the count. 
if    ($count < 1) { print "None\n";   }
elsif ($count < 2) { print "Unique\n"; } 
else               { print "$count\n"; }