Boolean less, greater, less than or equal, and greater than or equal. Each operator produces 1 if the condition is true, 0 otherwise. These operators may be applied to strings as well as numeric operands, in which case string comparison is used.
An example is:
if {$msglength > 0} then {
if { [string first , $idtext]<=0 } then {
append idtext ","
set msglength [expr $msglength+1]
}
}