E0004: a literal that is not well formed

Numeric, duration, date and direct-address literals have fixed shapes (Ed.3 6.3, Tables 5, 8 and 9, and 6.5.5 for % addresses). Examples that are refused:

x := 3#12;         (* bases are 2, 8 and 16 *)
x := 16#;          (* no digits *)
t := T#;           (* no duration *)
a AT %IY0 : BOOL;  (* areas are I, Q and M; sizes X, B, W, D and L *)