When applied to a term list [q1;...;qn] and a theorem
A |- !p1...pn. t, the inference rule SPECL returns the theorem
A |- t[q1/p1]...[qn/pn], where the substitutions are made
sequentially left-to-right in the same way as for PSPEC.
A |- !p1...pn. t
-------------------------- SPECL "[q1;...;qn]"
A |- t[q1/p1]...[qn/pn]
It is permissible for the term-list to be empty, in which case
the application of PSPECL has no effect.