[expr] bit-wise "xor" operator

Arguments must be integers, result is an integer.

Bit ''n'' of the result is 1 if bit ''n'' of the two arguments differ. Otherwise, bit ''n'' of the result is 0.

**Examples**

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% expr 0b010 | 0b000
2
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[[So, what do I need to add to this example so the result is binary as well?  
Some sort of [format] - but I don't see a binary conversion sequence in the docs...]]
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