Data::Dumper is sometimes your very best friend.

use Data::Dumper; 
use Carp;
unless(defined($name)){
print STDERR Data::Dumper->Dump(
  [$input, $name,$num,$addr,$date,$n],
  ["input", "name", "num", "addr", "date", "n"]);
croak"Now let's stop and have a look at this...";
}
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The first time the program encounters what you have determined to be the error-condition, it will now print out the line of data and the variables extracted from it, and then conveniently fall-dead.