my %which;
do { push @{ $which{$_} } => "array1" } for @array1;
do { push @{ $which{$_} } => "array2" } for @array2;
do { push @{ $which{$_} } => "array3" } for @array3;
 
my @pairs = @array4;
while (my ($one,$two) = splice(@pairs,0,2)) {
     print "$one and $two are in (@{$which{$one}}) and (@{$which{$two}}) respectively\n";
}