Does bash have a tool ?

[Richard Owlett <rowlett@cloud85.net>]

My eventual goal is to create a personalized FAQ.
To that end I've collected all my outgoing mail which DOES NOT have 
"Re:" in the Subject into a single file {used standard SeaMonkey tools}.

Using a text editor's search&replace function I've placed "KEY1" at the 
beginning of the body of each message. Similarly, I've placed "KEY2" at 
the end of each body.

Searches led to <http://www.dsl.org/cookbook/cookbook_16.html> which 
describes tools to do word frequency tasks, primarily with bash builtins.

First I need to eliminate the irrelevant text between "KEY2" of the 
previous message and "KEY1" of the message of interest. It should be 
straight forard to do in BASIC.

But is there an already tested function for that?
TIA