You cannot easily redefine these selectors:

#(#caseOf: #to:do: #ifNotNil: #ifNil:ifNotNil: #whileTrue: #ifNotNil:ifNil: #ifFalse: #timesRepeat: #whileTrue #caseOf:otherwise: #whileFalse: #ifNil: #to:by:do: #ifTrue: #ifFalse:ifTrue: #or: #whileFalse #ifTrue:ifFalse: #and:)

You can redefine those selectors but depending on the send site, the redefined method is used or not.

One trick is to have the send site in a method / class with compilation options disabling the inlining of the selectors you want.

Another trick is to use a pattern different slightly that the optimized pattern, for example, I believe that Marcus changed #and: so:

a and: [ b ] -> and: is optimized at compile time, send site won't use overridden method.

a and: [ :x | b ] -> and: is not optimized at compile time, send site will use overridden method.

Maybe it works with #or: too.

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