> (set 'str "alphabet" 'n 2 'm 4)
4
> ; starting from n characters in and of m length
> (slice str n m)
"phab"
> ; starting from n characters in, up to the end of the string
> (slice str n)
"phabet"
> ; whole string minus last character
> (chop str)
"alphabe"
> ; starting from a known character within the string and of m length
> (slice str (find "l" str) m)
"lpha"
> ; starting from a known substring within the string and of m length
> (slice str (find "ph" str) m)
"phab"