Idea Summary
The database provides a native REPLACE function but no native function for easily performing a search and replace on a CLOB. The idea is to create an APEX_STRING_UTIL.SEARCH_AND_REPLACE function that works for CLOB datatypes. 

Use Case
Performing search and replace on CLOB data types. This would be helpful for searching and replacing text in HTML content stored in a CLOB.

Preferred Solution (Optional)
Create a new APEX_STRING_UTIL function called REPLACE_AND_REPLACE. Pass in a CLOB, an array of search terms, and an array of replace terms. e.g. 

l_new_clob := 
  APEX_STRING_UTIL.SEARCH_AND_REPLACE 
   (p_source  => l_source_clob,
    p_search  => apex_t_varchar2 ('HELLO','GOODBYE'),
    p_replace => apex_t_varchar2 ('Hello','Goodbye'));