Here some syntax related articles I found helpful while still working with TCL/expect scripts in networking environments.

The 1-st method to debug a expect scripts is done by setting exp_internal 1 in the script itself

exp_internal 1

The 2-nd debug method is adding -d command line option for executing the script

expect -d script.exp

Commenting out a passage in a expect script works like that:

set COMMENTED_OUT {

        commented out stuff

}

or

proc COMMENTED_OUT {} {

        commented out stuff...

}

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