Actually you can:
- if the variables are smaller than the registers. In x86 there are even registers that 'look' into others - AX = AH + AL, etc
- (exotic) if mentioned 4 registers are general-purpose registers and veriable sizes are the same as registers - there's probably also an instruction pointer register, so do a jump to the fifth variable like an address - and you'll have all 5 stored in registers for some period of time before the crash