@union = ((SDT,`1781183799.44927\',-----),

##</code><code>##

@union = (['SDT','1781183799.44927\','-----'],
          ['BN','1781183799.44972\','-----'],
          ['BNN','1781183799.46753\','-----']);

##</code><code>##

my @diff;
my @inter

my %count2 = ();
foreach my $element (@union,@ICUNAV) {
  my $k=join '',@$element; 
  $count2{$k}{COUNT}++;
  $count2{$k}{ELEMENT}=$element;
};
foreach my $element (keys %count2) {
  push @{ $count2{$element}{COUNT} > 1 ? \@inter : \@diff }, $count2{$element}{ELEMENT};
};
print Dumper(@diff),"\n";