What do I do now?

The old fashioned method is to RTFS which you will find at Perl/site/lib/PPM/UI.pm. I found this file simply by greping for the error message. Here is the code in question.

# Find the correct target for this package. This means matching the
# LANGUAGE tag in the PPD. Basically we find out what LANGUAGE the PPD
# represents, and we search through the targets looking for a subset w
+hich
# implement that language. If more than one target implements the lang
+uage
# and version, we pick the first. If none work, we fail. If the LANGUA
+GE
# tag is missing, or the LANGUAGE matches the given target, we use the
# given target.
# NOTE: because LANGUAGE is a child-node of IMPLEMENTATION, we _first_
+ have to
# search for an implementation that matches the target, _then_ we have
+ to
# verify that the target supports the LANGUAGE tag. If it does, we ret
+urn it,
# otherwise we go on to the next target.
sub choose_target {
    my $o = shift;
    for (@_) {
    # Load the target:
    my $target = PPM::UI::get_targ($_);
    next unless $target->ok;
    $target = $target->result;

    # Load the PPD and find a suitable implementation for this target:
    $o->make_complete($target);
    my $ppd = $o->getppd_obj($target);
    return $ppd unless $ppd->ok;    # the package doesn't exist.
    my $impl = $ppd->result->find_impl($target);
    next unless $impl->ok;
    my $lang = $impl->result->language;

    # Older PPDs didn't have a LANGUAGE tag, so we must assume a Perl
    # implementation. For old-times' sake, we'll assume version 5.6.0 
+is
    # required.
    unless (defined $lang) {
        $lang = PPM::PPD::Language->new({
        NAME    => 'Perl',
        VERSION    => '5.6.0',
        });
    }

    # Check if this implementation's language is understood by the tar
+get:
    my $match = $lang->matches_target($target);
    return $match unless $match->ok;
    return Ok($target) if $match->result;
    }
    return Error(
    "no suitable installation target found for package $o->{name}."
    );
}
[download]

So the error relates vaguely to the (lack of) a LANGUAGE attribute. As you can perhaps see if there is not a LANGUAGE tag in the PPM then it runs some default code. This is the code that is executing to give you the error message. This is a good place to put in some debugging print/warns so you can see what is going on. It may be as simple as adding a LANGUAGE tag to the PPD or possibly changing the default version to 5.8.x to get a valid lang that will match the target.