Did you have a look at or try something like MIME::Parser? It seems to be able to do what you need without you having to code the parsing yourself.

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

Im already using that. What I need to do, is to get the generated data in name => value format, for input to Sendmail::PMilter.

If PMilter could accept a opaque header object, I would just pass the output from MIME::Parser to PMilter, but now I need to use: $ctx->Addheader(NAME, VALUE)

thus I need to have access to indivual header lines in a way that makes it possible to iterate over the headers.

Any folding must be kept as-is to keep the output RFC compliant.

sebastiannielsen2:

You're losing your first character in the headers because that "\S". Maybe you should try something more like:

...roboticus

When your only tool is a hammer, all problems look like your thumb.

How would that work? A folded header line does contain one single \n, and then the next line begins with any whitespace. A newline (\n) followed by a non-whitespace is the beginning of a new header.

The whitespace a folded line begins with, may not neccessarly be a \n. In face \n would not be permitted, because a double \n (\n\n) would mark the start of body

Example of a non-folded header line, combined with a folded header line combined with a non-folded one:

Subject: Hi you are beutiful
Content-Type: text/plain;
    format=flowed;
    charset="iso-8859-1";
    reply-type=original
Return-Path: <example@example.org>
[download]

This should result in:

$fixedheaders[0] = "Subject: Hi you are beutiful";
$fixedheaders[1] = "Content-Type: text/plain;\tformat=flowed;\tcharset
+=\"iso-8859-1\";\treply-type=original";
$fixedheaders[2] = "Return-Path: <example@example.org>";
[download]

sebastiannielsen2:

In that case, I'd use:

@fixedheaders = split /\n\b/, $fixedmsgheader;

Update: checked my work with a test program:

 cat splitest.pl
#!/usr/bin/env perl
use strict;
use warnings;

my $t = q{
Subject: Hi there
Content-Type: text/plain;
    format=flowed;
    charset="iso-1189-1";
Return-Path: <example@example.org>
};

my @fields = split /\n\b/, $t;
print join("\n***\n", @fields), "\n";

localadmins-MacBook-Pro-2:~ [mmason]
$ perl splitest.pl

***
Subject: Hi there
***
Content-Type: text/plain;
    format=flowed;
    charset="iso-1189-1";
***
Return-Path: <example@example.org>
[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.

OOps the result was a Little bit wrong. It should be:

$fixedheaders[0] = "Subject: Hi you are beutiful";
$fixedheaders[1] = "Content-Type: text/plain;\n\tformat=flowed;\n\tcha
+rset
+=\"iso-8859-1\";\n\treply-type=original";
$fixedheaders[2] = "Return-Path: <example@example.org>";
[download]

Eg with newlines Before the tabs.

What about good ol' line by line processing?

use strict;
use warnings;
use Data::Dumper;

my $t = q{
Subject: Hi there
Content-Type: text/plain;
    format=flowed;
    charset="iso-1189-1";
Return-Path: <example@example.org>
};

my @fields;
for ( split /\n/, $t ) {
  push @fields, $_ and next if /^\S+:/;
  $fields[-1] .= $1 if /\s*(.+)/;
}
print Dumper \@fields;
[download]

I tried with the following:

@fixedheaders = split(/\n\S/, $fixedmsgheader);

But that eats the first char in header lines.

Have you tried using a look-ahead?

@fixedheaders = split(/\n(?=\S)/, $fixedmsgheader);
[download]

Not tested, but that should stop the regex consuming the first character.

Hi there!

I propose use perl regexp positive look ahead:

split /\n(?=\S)/, $fixwdmsgheader;

p.s.: also please look at: Email::MIME - mail rfc have a lot of hidden issue/s

good luck!