if ($alphabet{$s} % 2) {

##</code><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);

##</code><code>##

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