Hi, thanks for your advice but I am using strict! Is this any better?? It atill doesn't work right ;-(

 sub calc_enthalpy   {

                      my ($hash, $enthalpy_hash) = @_;
                      my (@common, @total);

                             foreach (keys %$enthalpy_hash)      {


                                      if (exists $hash->{$_})    {
                                              push @common, "$_ = ", $
+enthalpy_hash->{$_} * $hash->{$_}, "\n";
                                              push @total, $enthalpy_h
+ash->{$_} * $hash->{$_}, "\n";
                                       }

                                    return (\@common, \@total);

                             }

   }
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