.Q.A       / upper-case alphabet
.Q.a       / lower-case alphabet
.Q.an      / all alphanumerics

Strings: upper-case Roman alphabet (.Q.A), lower-case Roman alphabet (.Q.a), and all alphanums (.Q.an).

q).Q.A
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
q).Q.a
"abcdefghijklmnopqrstuvwxyz"
q).Q.an
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789"