In Tcl 8.5, the expr command has a variadic min() function.
% expr min(5,1,4,2,3) 1 % expr min(5,1.1,-17.345,1e10) -17.345
All arguments to the min must be able to be interpreted as numeric. Otherwise, you get this sort of error:
% expr min(5,7,1,-6,a,19)
invalid bareword "a"
in expression "min(5,7,1,-6,a,19)";
should be "$a" or "{a}" or "a(...)" or ...