I thought I may be worth mentioning the extra element required to get 2-D position text, search for "Cargo-cult" below:

{       
    package Text;
    BEGIN{ @Text::ISA = qw/PDL::Graphics::TriD::Object/;}
    use PDL::Graphics::OpenGLQ;
    use PDL::Graphics::OpenGL;
    
    sub new { 
        my ($class, $text, $x, $y) = @_;
        my $lb = PDL::Graphics::TriD::get_current_window
                                               ->glpRasterFont("8x13",
+0,255);
        bless { lb => $lb, text => $text, posn => [$x,$y,0] }, $class;
    }                                          
                                               
    sub togl {
        my $self = shift;

        # Cargo-cult:  
        # http://glprogramming.com/red/chapter08.html
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluOrtho2D(0.0, 1.0, 0.0, 1.0);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        
        glDisable(&GL_LIGHTING);
        glColor3f(1,1,1);
        my @posn = @{ $self->{posn} };
        glRasterPos3f($posn[0], $posn[1], $posn[2]);
        PDL::Graphics::OpenGL::glpPrintString($self->{lb}, $self->{tex
+t});
        glEnable(&GL_LIGHTING);
    }
}
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