::tcl::mathop::< implements the less than functionality of the < operator in expr.
< returns 1 if all its arguments are ordered, left-to-right, and 0 otherwise. If no arguments are given, it returns 1, since there is nothing that is unordered. < compares values numerically if possible, and otherwise falls back to comparing them in the manner of string compare.
Example
< 1 3 5 2 7 ;# -> 0 < aardvark bat canary ;# -> 1
In expr, < is strictly a binary operator:
expr {$a < $b}
Otherwise, simple string comparison (as in string compare with no options) is used.