let match2 s1 s2 =
let len1 = String.length s1
and len2 = String.length s2 in
if len1 < len2 then false else
let rec aux i =
if i < 0 then false else
let sub = String.sub s1 i len2 in
if (sub = s2) then true else aux (pred i)
in
aux (len1 - len2)