use v6;
my @array = < 1 3 4 55 4 3 4 22 1 3 4 3 2 2 3 34 >;

my @y = @array.classify({$_})\
              .categorize({ .value.elems==1 || Nil }).[0].value».key;

say "{@y.sort.join(',')} are the numbers that appear only once" if @y;

#my @y = @array.classify({$_}).grep({ .value.elems == 1 })».key;