We could chosse not to interpolate %i, %d, ..., but interpolate all non used formats from printf like %hash, ... . (Most of the %i, %d, ... aren't even good names for hashes...)

Is "%dth" the name of a hash, or is someone trying to printf "7th"? This solution seems like a mess. Besides, I don't want perl to start telling me what I can and can't use as a name for a particular sort of variable. Seems too much like some other language.

It has always bothered me when people name their hashes %hash or, even worse, %hash_table. You wouldn't use $scalar or $variable, would you? I hope? Unless maybe it was a flag that told you whether some other piece of data was a scalar or a variable. The name of the variable should reflect how it's used in some way.