union_intersection_differences

use Data::TreeDumper ;

@a = (1,    3, 5, 6, 7, 8   );
@b = (   2, 3, 5,    7,    9);

# one loop
@union = @isect = @diff = ();
%union = %isect = %diff = ();

foreach $e (@a, @b) 
	{
	$union{$e}++ 
		? do { $isect{$e}++ ; delete $diff{$e} }
		: $diff{$e}++ ;
	}

@union = keys %union;
@isect = keys %isect;
@diff  = keys %diff ;

@a_diff = grep { $diff{$_} } @a ;
@b_diff = grep { $diff{$_} } @b ;

# one loop 2
@union = @isect = @diff = ();
%union = %isect = %diffs = ();

%keys = ( 0 => { map { $_ => 1 } @a}, 1 => { map { $_ => 1 } @b} ) ;

for $e (@a, @b) 
	{
	$union{$e}++ 
		? do { $isect{$e}++ ; delete $diffs{0}{$e} ; delete$diffs{1}{$e} }
    		: $diffs{$keys{1}{$e} // 0}{$e}++ ;
	}

@union  = keys %union;
@isect  = keys %isect;
@a_diff = keys %{$diffs{0}} ;
@b_diff = keys %{$diffs{1}} ;
@diff   = (@a_diff, @b_diff) ;