LFILL(x,a,n) is a string function that inserts the character string a (string literal) at the start of the character string x (string specification) as many times as necessary until the character string has reached length n (unsigned integer). Only expressions that produce an alphanumeric value are permitted as string specifications.

If the character string a cannot be completely inserted without exceeding the specified total length, only the part that is needed to reach the total length is inserted.