Right, I've been using Perl off and on for a few months, building bits of code as I go along. I never even did a GCSE in IT. I've never read a book about programing, had a lesson or anything. So in a nutshell, my coding is a mess. Here's an example of what I write - It's parsing code to take a set of lines and convert it into a csv. 
if ($#ARGV != 2){die "usage $0 filenamein filenameout\n";}
open( INFILE, "< $ARGV[0]" ) || die "Cannot open $ARGV[0] $!\n";
open( OUTFILE, "> $ARGV[1]" ) || die "Cannot open $ARGV[1] $!\n";
$nopat=0;
$lookup ="";
while (<INFILE>)               {
   $line=$_; 
 if($line=~m/^Patient ID.*?(\d+)/)    {
$ID=$1;    
$nopat=$nopat+1;
$blank="";

print $ID."\n";

%hash = ();
}
if($line=~m/^NAD.*?(\d+)/)       {
chomp;
$nhs=$1;
}

if($line=~m/^Date Of Birth/)       {
$dob=$line;
$dob=~s/Date Of Birth  ://;
chomp $dob;
}

if($line=~m/^Sex/)       {
$sex=$line;
$sex=~s/Sex  ://;
chomp $sex;
}



if($line=~m/^Post/)        {
$postcode=$line;
$postcode=~s/Postcode  :(\w+)/$1/;
chomp $postcode;
$lookup=$lookup.$ID.",".$nhs.",".$postcode.",".$dob.",".$sex."\n";
#$age = <STDIN>; # pause
#print $lookup;
}


if ($line=~m/^\d\d\/\d\d.*?/)  {
#print "$line";
@names = split(',',$line);
$date=@names[0];
$index=@names[1];
$nonsense=@names[2];
$val=@names[3];
$test=@names[3];
$orgtest=@names[3];
$orgindex=@names[1];

chomp $orgtest;
chomp $val;
chomp $test;
#print "$val\n";

#if  ($index=~m/O\/E -/) {
#$index=~s/\d.*//;  #search for digits and deletes everything after it
#}
$test=~s/\s$//; #substitute all blank spaces at end of line with nothi
+ng
$test=~s/\s$//; #substitute all blank spaces at end of line with nothi
+ng




#$index=~s/(\.\d+)|(\d+\.\d+)//;#delete number.number
$index=~s/(\d)(\.00)(\s)/$1.$3/; #delet     .00s 
$index=~s/(\d\.\d)(0)(\s)/$1.$3/; #delet     .x0s 
$index=~s/(\d)(\.0)(\s)/$1.$3/; #delet e.0s 
$index=~s/\s(\.\d)/0.$1/; #add a 0 in front of a period  This is so th
+at the units match the old units and that replace works



$index=~s/\<|(\)|\()|\/|\^|\.|\*|//g; #substitute all operators
$test=~s/\<|(\)|\()|\/|\^|\.|\*|//g; #substitute all operators
$test=~s/\s0//;
#$test=~s\s0$\\;
$testother="$test"."0";
$index=~s/\s$testother\s.*//;
$index=~s/\s$test\s.*//;



$presub=$index;
$index=~s/$testother//;
$index=~s/$test//;  #search for last 
#$index=~s/(\.\d+)|(\d+\.\d+)//;#delete number.number

#print "-$val-  substituted    -$index-  \n";


#index=~s/x109l|x109 L|109L|x1012L|gdL|iul|iuL|gdl|ugL|uL|gL|mmolL|mmo
+ll| Ul|1012L| gl |mmh|mm|.0|IUL|Uml|ngmL| UL//;

$index=~s/\s+$//; #substitute all blank spaces at end of line with not
+hing
$index=~s/\.$//; #substitute all . spaces at end of line with nothing
$index=~s/\s$//; #substitute all blank spaces at end of line with noth
+ing
$index=~s/(OE -\w*)\d/$1/; #substitute all blank spaces at end of line
+ with nothing
$index=~s/\s\d+\scm$//;





#$index=~ s/10\*.*//; #Search for 10*whatever and delete it
#$index=~s/x109l|x109 L|109L|x1012L//;

$val=~ s/mL\/min\/1.73m2//;
$val=~ s/10\*.*//; #Search for 10*whatever and delete it
$val=~s/109L//;


$val=~tr/[0-9][.]//cd;



#$index=~s/$val//; #and re dof or final clear up
$index=~s/\s+$//; #substitute all blank spaces at end of line with not
+hing
# print "-$test-  substituted    -$index-  \n";

if ($val != "")  {
$hash{$index} =$hash{$index}.$val.",";
#push @lines, $ID.",".$index.",".$date.",".$val.",".$orgtest.",".$orgi
+ndex.",".$presub.",".$test.",".$testother."\n";  #HanDY TO TEST
push @lines, $ID.",".$index.",".$date.",".$val."\n";  #HanDY TO TEST
push @keys, $index."\n";
}
}
}

#print "Sorting and collating records.....takes some time.....\n Wait 
+for this window to close before continuing \n ";
my @unique = ();
my %seen = ();
my @unique = grep { ! $seen{ $_ }++ } @keys;
@sorted = sort { $a cmp $b } @unique ;

#print @sorted;

print OUTFILE @lines;
print "\n$. lines of data Processed. ";
close (OUTFILE);
open( OUTFILE2, "> $ARGV[2]" ) || die "Cannot open $ARGV[2] $!\n";
print OUTFILE2 @sorted;
close (OUTFILE2);
close (INFILE);
$path="lookup.CSV";
open (OUTFILE3, "> $path") || die "Cannot open LOOKUP.CSV $!\n";
print OUTFILE3 $lookup;
close (OUTFILE3);

[download]
So - what basic errors am I making. Basically all the above is cobbled together. What should decent code look like??

In reply to Code Critique by rhiridflaidd

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