tie @l, "Tie::File", $file or die $!;
for my $i (0 .. $#l) {
    if ($l[$i] =~ /Error Occurred/) {
        while($i > 0) {
            $i--;
            if ($l[$i] =~ /(A|B):\d+/) {
                print $l[$i];
                exit; # or last
            } elsif ($l[$i] =~ /^====/) {
                exit; # or last
            }
        }
     }
}