SQL & PL/SQL

Hi.
I have a problem.
I need to get a part of multiline string. e.g. everything between 'str_begin' and 'str_end'
If line is one it works fine:

SQL> select regexp_substr('asdfas str_begin fdfd str_end  fasdg','str_begin.*str_end') from dual;

REGEXP_SUBSTR('ASDFASS
----------------------
str_begin fdfd str_end

But if there two lines:

SQL> select regexp_substr('asdfas str_begin fdfd
                      str_end  fasdg','str_begin.*str_end') from dual;  

R
-

Is it possible to get everything between 'str_begin' and 'str_end' if these tags are in different lines?