my @file_and_signals1 = qw/AA BB CC/;
my @file_and_signals2 = qw/22 BB 33 44/;
my @file_and_signals3 = qw/jj BB CC kk oo pp 99/;
my @file_and_signals4 = qw/xx kk ll/;


my %count_hash;

for my $a (
  \@file_and_signals1,
  \@file_and_signals2,
  \@file_and_signals3,
  \@file_and_signals4
)
{
   for my $w(@$a) {
      $count_hash{$w}++;
   }
}

while (my ($k,$v) = each %count_hash) {
  print "$k $v\n" if $v>1;
}