SQL & PL/SQL

Hi
I have a CLOB with some text.

DECLARE
  result CLOB;
BEGIN
result:='I need to replace this <my_tag>Everything can be here </my_tag>';
-- Some operation to replace '<my_tag>Everything can be here </my_tag>' with '<It works/>'
DBMS_OUTPUT.PUT_LINE(result); --I want 'I need to replace this <It works/>' to be here
END;

I do not know what text is between <my_tag> and </my_tag> but I need to replace it.
Is it possible?