whole(string) is in a fld

[FlexibleLearning at aol.com]

I am trying to write a function that returns whether a given phrase  exists 
in a field as whole words.
 
e.g.
put "This is a test." into fld 1 (note the punctuation)
 
whole("This is a tes",fld 1)  = FALSE 
whole("This is a test",fld 1) = TRUE.
 
A bit like trying to get the line "This is a tes" is among the words of fld  
1 to work (obviously it doesn't), even assuming no punctuation were  involved!
 
I've returned to this little conundrum many times over the years but have  
yet to solve it.
 
Any offers?
 
/H