That's the line I create RecDescent module object : my $p=Parse::RecDescent->new($grammar) It the goes inside RecDescent.pm file - running 'sub new' and fails towards the end where it tries to call '$self->Replace' . I can see the 'Replace' subroutine a few lines below! Why can't it find the subroutine in the same file and same package? It found 'sub new' for the module successfully!!!