Ah, your programs are becoming complex enough that the realization that there are always 2 people who need to understand the code is starting to sink in. Those 2 people are: (a) you when you write it and (b) you when you have to extend it or fix at some time in the future! And if it is a useful program, one of these 2 things and probably both will happen!

Some simplifications to the code will be possible, based upon your first example, I recoded the first part with some straightforward techniques and with just borrowing pretty much your regex'es. Your actual record is more complex. However, I hope that the lesson about spacing and indenting is becoming more clear - it helps a LOT. 

#!/usr/bin/perl -w
use strict;

my $patient_id;   #patient record for the CSV file
my $nhs;
my $dob;
my $sex;
my $postcode;

my $total_patients=0;
while (<DATA>)
{
   s/^\s*//;  #remove leading space
   s/\s*$//;  #remove trailing space
   
   $patient_id = $1 if m/^Patient ID .*?(\d+)$/;
   $nhs        = $1 if m/^NAD .*?(\d+)$/;
   $dob        = $1 if m/^Date Of Birth .*?([\/\d]+)$/;
   $sex        = $1 if m/^Sex .*?(\w+)$/;
   
   #record ends with postal code -> output to the CSV file
   
   if ( ($postcode )= m/^Postcode .*?(\w+)$/ )
   {
      print "$patient_id,$nhs,$postcode,$dob,$sex\n";  #CSV line
      
      $total_patients++; # this is here instead of with $patient_id
                         # because it is here that we have an 
                         # "official"  patient record
      
      # this starts variables "over again". A runtime warning will
      # happen if for some reason one of these winds up still
      # being undefined when the record is printed to the CSV file
      #
      # note: doing this for $postcode is not necessary, but I
      # treat this variable same as the others because this lessens
      # the chance of a mistake when modifying the program later.
           
      $patient_id = $nhs = $dob = $sex = $postcode = undef;           
+           
   }   
}   

print "Total Patients: $total_patients\n";

=prints
1234,5678,BH78,01/01/1965,yes
4321,999,XYZ98,10/10/2007,no
Total Patients: 2
=cut

__DATA__
Patient ID 1234
NAD 5678
Date Of Birth : 01/01/1965
Sex  : yes
Postcode  : BH78
Patient ID 4321
NAD 999
Date Of Birth : 10/10/2007
Sex  : no
Postcode  : XYZ98

[download]

In reply to Re^3: Code Critique by Marshall
in thread Code Critique by rhiridflaidd

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.