if ($mySellfirstflag eq "YES") {
    %Sellhash = ($sedol => $shares); 
    #Do you mean that with mySellfirst that we should replace the shar
+es,
    #If so, the above line should be $Sellhash{$sedol}=$shares.
    #As it stands now, we replace the entire hash!!

##</code><code>##

      $Sellhash{$sedol} = $shares; #You did a .= here was that a typo?