It appears highly likely that you have a non-matching part of the regex that results in an undefined value some of the time. I would use something like code below to debug things. This assigns all of the individual var names into one array (@result) and avoids a mess with specifying each var name.

Run this on your data set and you see what it matching and what is not. Undefined is a "value" and I don't think that just checking scalar @result is enough. Anyway this should show where the program is failing to match, presumably on line 14 of the input.

my @result =   # note @ variable not $variable !!
(($beginning, $agency, $district, $ssn, $serv_per_m,
  $serv_per_y, $serv_per_t,.............);

while (<IN>)
{

   print;
   my @result = (.....blah) #see previous posters code
   my $token_nr=0;
   foreach my $token (@result)
   {
       $token_nr++;
       if (defined ($token) )            #if you try to print an undef
       {                                 #program will bomb
          print "$token_nr++\t$token\n"; #this allows you to see exact
+ly
       }                                 #what is undef without progra
+m
       else                              #bombing
       {
          print "$token_nr++\tUNDEFINED\n";
       }
   }
}
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I suspect that your regex is too restrictive. Also fixed column files aren't that common but you may indeed have one. (\D) matches exactly one non-digit charater, to allow say somewhere between 1 and 4 non-digit characters, use (\D{1,4}). for a character set, use say  ([\d-]{9,11}) if ssn could be either 123-45-6789 or 123456789. Use \s* to indidicate zero or more space characters.