expr right shift operator; only applies to integer arguments.

Equivalent to dividing the first argument by 2 n times (i.e., /(2**$n)), where n is the second argument.

[DKF: Is this an arithmetic or logical shift? I think it might be an arithmetic one, as it is well-defined on negative numbers with bignums]

AMG: Definitely arithmetic. [expr {-1 >> 1}] gives -1, not 2147483647 or any such thing.