#!/usr/bin/perl -n

BEGIN {
    use strict;
    use warnings;
    #use Data::Dumper;

    my $filename = $ENV{FILENAME};
    unless (defined($filename)) {die "No filename in environment (filename)\n";}

    @ARGV = $filename;

    my $flag = '0';
    my @lines;
    my $whole_match;
    my @part_before_match;
    my @part_after_match;
    my @number_of_matches;
}

if ( $_ =~ m/<Text>/ ) {
    $flag = '1';
}

if ( $flag == '1' ) {
    $_ =~ s/\r\n//;
    $_ =~ s/\n//;
    $whole_match = $whole_match . $_ . " ";
    if ( $_ =~ m/<\/Text>/ ) {
        $flag = '0';
        @number_of_matches = $whole_match =~ m/(Text>)/g;
        if ( scalar(@number_of_matches) > 2 ) { 
            die "More then one Text in one line.";
        }
        @part_before_match = $whole_match =~ /(.*)(?=<Text>)/;
        @part_before_match->[0] =~ s/^ *$//g;
        @part_after_match = $whole_match =~ /(?<=<\/Text>)(.*)/;
        @part_after_match->[0] =~ s/^ *$//g;
        $whole_match =~ s/[^<]*<Text>//;
        $whole_match =~ s/<\/Text>.*//s;
        @lines = $whole_match =~ m/(.{1,4})/g;
        if ( defined @part_before_match &&  @part_before_match->[0] ne "") {print "@part_before_match\n";}
        #print Dumper @part_before_match;
        foreach my $line (@lines) {
            print "    <Text>$line</Text>\n";
        }
        if ( defined  @part_after_match && @part_after_match->[0] ne "") {print "@part_after_match\n";}
        #print Dumper @part_after_match;
        undef @lines;
        undef $whole_match;
        undef @part_before_match;
        undef @part_after_match;
        undef @number_of_matches;
    }
}
else {
    print;
}

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

local $/ = '';
my $data = <DATA>;

do {
  $data =~ m|(<Text>.+</Text>)|s;
  my $prepared_string = prepare_string($1);
  $data =~ s/$1/$prepared_string/s;
} while($1);

print Dumper $data;

## subs ##
sub prepare_string {
  my $string = shift;
  $string =~ s/\n|<Text>|<\/Text>//g;
  
  my $chunk_size =  4;
  my $prepared_string;
  for (my $i = 0; $i <= length($string); $i=$i+4)  {
    my $part = substr($string, $i, $chunk_size);
    $prepared_string .= "<Text>$part</Text>\n";
  }
  return $prepared_string;
}

__DATA__
<Feld><Text>Hallo liebe Perl-Gemeinde,
ich wünsche euch ein schönes Fest und
einen guten Rustch ins neue
Jahr.</Text></Feld><Sig>
abc</Sig>

stefan@stefan-laptop:~/perl$ perl sort.pl
$VAR1 = '<Feld><Text>Hall</Text>
<Text>o li</Text>
<Text>ebe </Text>
<Text>Perl</Text>
[...]
<Text>ins </Text>
<Text>neue</Text>
<Text>Jahr</Text>
<Text>.</Text>
</Feld><Sig>
abc</Sig>
';

@match = $data =~ m|(<Text>[^<]*</Text>)|sg;
foreach my $m (@match) {
    my $prepared_string = prepare_string($m);
    $data =~ s/$m/$prepared_string/s;
}

#!/usr/bin/perl
use strict;
use Data::Dumper;
use warnings;

local $/ = undef;
my $data = <DATA>;
my @match;

@match = $data =~ m|(<Text>[^<]*</Text>)|sg;
foreach my $m (@match) {
    my $prepared_string = prepare_string($m);
    $data =~ s/$m/$prepared_string/s;
}

print $data;

## subs ##
sub prepare_string {
  my $string = shift;
  $string =~ s/\n|<Text>|<\/Text>//g;
  
  my $chunk_size =  10;
  my $prepared_string;
  for (my $i = 0; $i <= length($string); $i=$i+$chunk_size)  {
    my $part = substr($string, $i, $chunk_size);
    $prepared_string .= "<Text>$part</Text>\n";
  }
  return $prepared_string;
}

__DATA__
<Feld><Text>Hallo liebe Perl-
Geme(i)nde.

diesmal mit leerzeile
</Text></Feld><Sig>
abc</Sig>
<Text>V[iel]e Grüße
leo11</Text><Text>ps.: schönen abend</Text>

$data =~ s/$m/$prepared_string/s; 

if ( {<Text>} ..  {</Text>}