You will be warned for your question format.

There seems 2 problems, one is about error log and anothoer is about here document like printing. At first, your program prints anything or not? If you pickup troubled lines into sample script, I can know your $r->print() prints anything or not... at least in my environment.

I can print $r->print with configuration like this.

#mod_perl test
LoadModule perl_module /usr/local/libexec/apache22/mod_perl.so

#there should be better way than this...
<Perl>
unshift @INC, '/usr/local/www/apache22/cgi-bin/test-modperl';
</Perl>

PerlModule test1::sample
<Directory /usr/local/www/apache22/cgi-bin/test-modperl/test1>
    SetHandler perl-script
    PerlHandler test1::sample
</Directory>
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And $r->print in test1/sample.pm prints my text. I'm on FreeBSD 8.2, mod_perl2.0.5 .

package test1::sample;
use strict;
use warnings;

#old use Apache::Constants qw(OK);
use Apache2::Const qw(OK);

use Apache2::RequestRec();
use Apache2::RequestIO();

sub handler {
    my $r=shift;
    #old $r->send_http_header("text/plain");
    $r->content_type("text/plain");
my $a=<<EOS
test
test
test
EOS
;
    $r->print($a);
    return OK;
}

1;
[download]

good luck for you. regards.