expr logical "or" operator, counterpart to &&. Returns falsity if both arguments are boolean false, and truth otherwise. Note that this operator short-circuits, and does not evaluate its second argument if the first is true. See | for bitwise "or".
Note that this operator does not have a command equivalent in tcl::mathop; use the if command instead.
While there is no tcl::mathop equivalent, tcl::mathop::+ will give the desired result provided all arguments have been reduced to the "most basic" boolean values (non-zero or 0), like for instance when evaluated with any kind of boolean operator. For example, the following code
::tcl::mathop::+ {*}[lmap elem $listOfNumbers { expr {$elem > 10} }]
will tell you if any number element in $listOfNumbers is greater than 10. (See Faking tcl::mathop::&& and ||.)