undef is not-equal to “an empty string.”

Therefore, each of your if statements evalues to true, and the variable gets incremented several times.

Use the defined() function to check for a NULL field value, which comes across as undef.

Be sure not to use an “empty string” value in a text column, unless “an empty string” is a plausible, non-NULL possibility in your application.   (Unlikely.)

As for myself, I am not a fan of using the || alternate_value syntax.   Although you might think of it as being a check for NULL, it is in fact a check for anything that evaluates to a false value according to whatever rules Perl may have.   Which is why you see stuff like this in my code:

do { 
     $$rec{$_} = "foo" unless defined($$rec{$_}) 
   }
   foreach qw(FIELD1 FIELD2 FIELD3);
[download]

There are many ways to write it, of course, but the idea is clear:   for an arbitrarily-long list of field names, if any of the returned values is undef a specific value is substituted for them.   (Since this is, of course, being applied against the in-memory (not tied) hash returned by DBI::fetchrow_hashref, it does not modify the database in any way.)

This uses the foreach modifier exactly as described in perldoc perlsyn.