sub flatten {
  my %seen;
  my @temp = @_;
  for (my $i=0; $i < @temp; $i++){
      if ( UNIVERSAL::isa($temp[$i], 'ARRAY') ){
        die "Circular reference! Bailing..." if $seen{$temp[$i]}++;
        splice (@temp, $i, 1,  @{$temp[$i]} ) 
      }
  }
  return wantarray ? @temp : \@temp;
}
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