Here is a short example using formline and the accumulator based on your code. I simplified the INHALT format because I wasn't fully sure what you wanted to do with the ~~:

    #!/usr/bin/perl -w

    use strict;

    # Store the formats in variables

    my $header = << 'HEADER';
    Menge Art.nr. Bezeichnung Preis(?) Gesamt(?)
    __________________________________________________________________
+___
    HEADER


    my $body = << 'INHALT';
    @<<<< ^<<<<<<<< ^<<<<<<<<<<<<<<<<<<<<<<<<<< @>>>>>>>>> @>>>>>>>>>
    INHALT


    my $footer = << 'FOOTER';
    __________________________________________________________________
+___
    Warenwert: @>>>>>>>>>
    FOOTER


    # Sample data
    my @bestellung = ('Text one|1|3.99|7',
                      'Text two|2|5.49|8',
                      'Text three|3|7.89|9');


    formline($header);

    foreach (@bestellung) {
        my ($text, $nr, $preis, $menge) = split /\|/;
        my $summe = sprintf("%.2f", $menge*$preis);
        formline($body, $menge,$nr,$text,$preis,$summe);
    }

    formline($footer, 1234);


    print $^A; # Print the accumulator
    $^A = '';  # Clear the accumulator

    __END__

    prints:


    Menge Art.nr. Bezeichnung Preis(?) Gesamt(?)
    __________________________________________________________________
+___
    7     1         Text one                          3.99      27.93
    8     2         Text two                          5.49      43.92
    9     3         Text three                        7.89      71.01
    __________________________________________________________________
+___
    Warenwert:       1234
[download]

See also Re: Formats and Variable Scope and Re: format and IO::String.

--
John.