Would you please explain which is the difference between "replaced by and replaced with"? I have seen both forms!

Example: the term "should" was replaced with (or by) would

Thanks in advance!
I too am an English learner but I don't feel a big difference between 'replace with' and 'replace by'. Personally I like better the expression 'replace with'. The only case I would prefer 'replace by' is in a passive construction where someone is taken over his post by other person. "Mr Collin Powell will be replaced by Ms Condolezza Rice."

I'm not sure but I suppose:
replace by - to remove (or to take out) the original thing and put instead of it something another
replace with - (if there are 2 things, for example) each thing takes the place of the other one so that both remain (but change theit places)
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Hi Maverick!

I appreciate your help! Thanks!!
 paco2004's reply was promoted to an answer.