The Control Flow

If Condition

if { test1 } {
body1 
} elseif { test2 } {
body2 
} else {
bodyn
}

If you don't like the curly brackets, you can take them out. But then, you will have to give the full thing in one line. I know that after you had a look at that syntax, you are still wondering what in the world that was. Don't worry - an example will set things straight.

#The marriage status script...
#Change the status please
set marital_status "After"

label .thesis -text "Marriage is a three ring circus..."

if { $marital_status=="Before" } {
set ring "Engagement"
} elseif { $marital_status=="During" } {
set ring "Wedding"
} else {
set ring "suffe -"
}

label .proof -text "$marital_status Marriage: $ring ring"

pack .thesis
pack .proof

Run this script and give the 'marital_status' to "Before", "During" and "After" and see the different results.

You will need operators to do the checking. Fortunately, the operators in Tcl are same as in any other language. So a small experience with any language will guarantee that you know all them.