could this be what you want ?

# cat re1
use warnings;
use strict;

undef $/;
my $tout = <DATA>;
my $z;

while ($tout =~ /((?:DES|TN).+?(DATE|ZONE)[^\n]+\n\s*\n)/sg) {
         print "\n\n", ++$z, ":\n", $1;
}

__DATA__
DES  MAIL
TN   001 0 02 00
TYPE SL1
CDEN DD
CUST 0
KLS  1
FDN
TGAR 0
LDN  NO
NCOS 0
     09
DATE  9 MAR 2000

TN   001 0 02 01
     05 RLS
     06 TRN
     07 AO3
     08
     09
ZONE 002

TN   001 0 02 01
     05 RLS
ZONE 001
     07 AO3
     08
     09
DATE  9 MAR 2000
[download]

# perl -w ./re1


1:
DES  MAIL
TN   001 0 02 00
TYPE SL1
CDEN DD
CUST 0
KLS  1
FDN
TGAR 0
LDN  NO
NCOS 0
     09
DATE  9 MAR 2000



2:
TN   001 0 02 01
     05 RLS
     06 TRN
     07 AO3
     08
     09
ZONE 002



3:
TN   001 0 02 01
     05 RLS
ZONE 001
     07 AO3
     08
     09
DATE  9 MAR 2000
[download]

That is exactly what I wanted. Thanks Not sure I understand why it works though. why does ->  [^\n] - match all the data after the DATE and ZONE to the end of line doesn't it just mean match a beginning of line and a new line?

Hi,

glad that i could help you.

The [^\n] is a negated character class. Here it represents all characters which aren't "newlines". The newline-characters remained, though undefined $/, still in your string.

The regex [^\n]+\n matches on 1-n non-newlines followed by a newline.

After this there can be 0-n whitespaces \s* followed by another newline. This is your blank-line.

greetings, tos

The first thing I noticed was that you are undefing $/. Apart from that just localising it it enough to set to undef, that is usually done when you are slurping the entire file.

The second thing I noticed was that you are using /smx.

If I am interpretung your snippet correctly, you are slurping the whole file, asking that . match \n (/s), asking that ^ and $ match either side of \n (/m), and then hoping that

/(^DES|^TN).*?/ will match just a single line, with the correct first 2 or 3 letters. It won't.

It will match starting at the first newline followed by DES or TN, but with go on to match the rest of the entire file as there is nothing to stop .*? matching.

By the time you get to your end criteria, the is nothing left for it to match against.

A lot of assumptions based on little evidence, but it does fit what I see:)

I now have:-

((?:^DES|^TN).*?(?:(?:DATE|ZONE)[ A-Z0-9]*)(?=$^$)?)
[download]

But given the data I posted earlier it still matches ZONE even when not followed by blank line.

Trying to use (?=$^$)? to say only match the previous pattern if followed by the first blank line.

But given data :-

TN   001 0 02 01
     05 RLS
ZONE 001
     07 AO3
     08
     09
DATE  9 MAR 2000
[download]

Only matches upto ZONE and not DATE.

Given the format of your data, you would be much better of using "paragraph mode". Ie. Setting $/ to '' rather than undef. The each read will give you exactly what (I think) you are trying to acheive with your regex.

Try this on your data to see what I mean, the see perlvar $INPUT_RECORD_SEPERATOR for the details.

#! perl -slw
use strict;

local $/ = '';
while( <DATA> ) {
    print "'$_'";
}
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---

Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller

You're on the right track, though I suspect that the +? might not be doing what you want it do. It would help to show us a few representative records.

Would something like

while ( /^((?:DES|TN).*?(?:DATE|ZONE)[ A-Z0-9]*)$^$/sm ) {
    # $1 is the matched record, without the blank line
}
[download]

Data looks as follows:-

DES  MAIL
TN   001 0 02 00
TYPE SL1
CDEN DD
CUST 0
KLS  1
FDN
TGAR 0
LDN  NO
NCOS 0
     09
DATE  9 MAR 2000

TN   001 0 02 01
     05 RLS
     06 TRN
     07 AO3
     08
     09
ZONE 002

TN   001 0 02 01
     05 RLS
ZONE 001
     07 AO3
     08
     09
DATE  9 MAR 2000
[download]