I never heard of OTRS, and just because (or maybe even especially because) it has "Open Source" in its main program name, that's no sign of good, mature or solid code.

The "most obvious" choice in trouble ticketing systems for Perl is RT, as it is used by Perl itself and by CPAN to track bugs in modules.

Another system I have administered (and not just used, as RT) is Bugzilla, the trouble ticket system used by the Mozilla team - it was at the time a bunch of monstrous CGI scripts that amazingly did what they were told to, but they weren't that manageable / changeable.

I know that this dosen't help you in your evaluation of OTRS, but it seems to me that you haven't seen more obvious choices than OTRS yet :-)

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ;    # The  
$d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider
($c = $d->accept())->get_request(); $c->send_response( new   #in the
HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' #  web
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