include xpllib;         \provides StrLen and StrFind

proc PMid(S, N, M);     \Print string at Nth character M chars long
char S, N, M, I;
[for I:= 1 to M do ChOut(0, S(N-2+I));
CrLf(0);
];

char S;
def  N=2, M=3;
[S:= "abcdefgh";
PMid(S, N, M);                  \starting from N chars in and of M length
PMid(S, N, StrLen(S)-N+1);      \starting from N chars in, up to end of string
PMid(S, 1, StrLen(S)-1);        \whole string minus last character
PMid(StrFind(S, "d" ), 1, M);   \starting from known char and of M length
PMid(StrFind(S, "cd"), 1, M);   \starting from known substring and of M length
]