Want to parse string by applying design patterns

We have a requirement to parse string (this string is coming by reading some file) in such a way that if its start/end (e.g. --Abc Start -- Abc End) with some specific string then all lines between those two should be stored in String list say s1 and rest in other String say s2. Want to solve this problem by using design patterns

123
456
--Abc Start
xyz
pqr
-- Abc End
789
101
--Abc Start
mno
efg
-- Abc End

So lines below should be stored in String list s1

s1[0]

xyz
pqr

s2[1]

mno
efg

And lines below should be stored in String s2

123
456
789
101

Tomorrow some other requirement might come to store specific line in different string or in string list.

thanks in advance

regards Amit.