if ($alphabet{$s} % 2) {
[download]

The problem must be here somehow, becase you're using the % operator only here. The warning indicates that one operand of % is undefined. 2 is a defined constant, so $alphabet{$s} must be undef. %alphabet mus have been filled somehwere else, you didn't show that code, $s comes from a very "ugly" part of your code:

foreach $record (@contents)  {
# where does @contents come from?
# you said a flat-file: why did you read the whole
# file into an array, if you did? is that neccessary?
# you'll probably rather like

while(defined(my $record = <$flatfilehandle>)){
    
    @fields = split(/\|/,$record);
# @fields is global? probably not
    my @fields = split...

    $tidm=$fields[0];$tidm=~s/\s+$//g;
    $nice=$fields[1];$nice=~s/\s+$//g;
#it's much easier to say
 my ($tidm,$nice) = split /\|/,$record;
# and it's more effective to drop the /g, for it's 
# completely useless: You cannot mach the EOString more 
# than one time. Correct me if these variables might 
# contain multiple lines, but i'm "quite sure" they don't 
# :)

    $s = substr($nice,0,1);
[download]

So now $s holds the first character of $nice. If $nice is empty, $s will be empty, too. Do you have the key '' in your hash %alphabet. $s may be any character (apart from '') depending on the input, are all cases covered in %alphabet? If not, consider assuming a default:

(defined $alphabet{$s} ? $alphabet{$s} : 0) % 2
# use exists() if all values of %alphabet are defined
[download]

thanks for the help, i will have to digest this for a while! I dont think $s can be empty, as the hash is automatic i think, there are no invalid records in flatfile, i will check... i may have things confused. if so i apologise! danke

Thanks very much, you were all quite right, the first iteration found no value ( uninitialised! doh! ) so i made it increment from 0 before i did stuff on it.. now it works fine... thanks perl monks!

$alphabet{$s}++;
    open (DATA, ">> ./ATOZ/$s.shtml" )or die "can't open file: $s!";
        if (($alphabet{$s}) % 2){
            print DATA qq|<tr bgcolor="#eeeeee">;
        } else {
            print DATA qq|<tr bgcolor="#FFFFFF">|;
        }
    close DATA;
[download]

I'd recommend adding a couple of sanity check statements right before your modulus test:

# what's in the %alphabet?
foreach my $letter (keys %alphabet)
{
  print "$letter\n$alphabet{$letter}\n";
}
# what's $s?
print "$s\n";<br>

# does a key/value pair exist in %alphabet for $s?
print "$alphabet{$s}\n";<br>
[download]

~CubicSpline
"No one tosses a Dwarf!"

thanks, i think it does have all i would expect.. but maybe a whitespace exists, i will check it out, thanks A, 309 B, 318 C, 292 D, 120 0-9, 11 E, 183 F, 146 G, 164 H, 161 I, 199 J, 93 K, 54 L, 132 M, 280 N, 112 O, 50 P, 193 Q, 25 R, 128 S, 339 T, 182 U, 51 V, 46 W, 101 X, 11 Y, 22 Z, 19

Is it issuing this warning multiple times for the same run? Otherwise: you get an error the first time through because you never set $alphabet{$s} to anything for its first use, but at the end of your sub, you ++ it, which means that thereafter it has a valid value (i.e. has been "initialized").

Yes, multiple times... I thought i had initialized it by saying: my alphabet; and then it would populate itself automatically...? thank you!