print prefix? "abcd" "ab"
print prefix? "abcd" "cd"
print suffix? "abcd" "ab"
print suffix? "abcd" "cd"

print contains? "abcd" "ab"
print contains? "abcd" "xy"

print in? "ab" "abcd"
print in? "xy" "abcd"

print index "abcd" "bc"
print index "abcd" "xy"