#!/usr/bin/perl 
use strict;
use warnings;   # the same as #!/usr/bin/perl -w in first line

while (<DATA>)
{
   next if /^\s*$/;     # skip blank lines
                        #   sometimes a last blank line
                        #   causes problems!
   s/\s*$//;            # or chomp;  fine also            
   
   my ($date, $description, $measurement) = (split (/,/,$_))[0,1,3];
   my ($value, $units) = split (/\s+/,$measurement);
   print "date     = $date\n",
         "descript = $description\n",
         "value    = $value\n",
         "units    = $units\n\n";

   # instead of print, do something here ...
}

=prints
date     = 20/08/2007
descript = Erythrocyte sedimentation rate
value    = 3
units    = mm/h

date     = 20/08/2008
descript = Total white blood count
value    = 6.7
units    = 10*9/L

date     = 04/04/2007
descript = Haemoglobin estimation 12.9 g/dL
value    = 12.9
units    = g/dL
=cut

__DATA__
20/08/2007,Erythrocyte sedimentation rate,,3 mm/h
20/08/2008,Total white blood count,,6.7 10*9/L
04/04/2007,Haemoglobin estimation 12.9 g/dL,,12.9 g/dL