To describe patterns taking into account the first tag of sentences, it will be possible to use the restriction <pos:0>. For instance:
SubjL : PRO<pos:0> VERB
%
This rule is applied when the subject pronoun is the first element of the sentence (position = 0).
It is also possible to use symbol `` ^ '' to represent a head that has no dependent elements to its left (apart from the dependents inserted in the pattern). For instance:
SubjL : ^ NOUN|PRO VERB
%
That means there is only a NOUN or a PRO linked to the verb as a left dependent. There are not other complements or modifiers linked to the verb in the sentence appearing to the left of the nominal subject.