I had a peek at the logs and I read something about $cgi (and maybe others) that it will not stay shared or so

You can't use my outside of subs in an Apache::Registry script. Refer to the mod_perl Guide. Possible solutions:

sub foo {
   my ($cgi, ...) = @_;
   ...
   $cgi->...
   ...
}

sub main {
   my $cgi = ...;
   foo($cgi, ...);
}

main();
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or

our $foo;

sub foo {
   my (...) = @_;
   ...
   $cgi->...
   ...
}

sub main {
   local $cgi = ...;
   foo(...);
}

main();
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