Y is an integer that selects options as follows.

If Y is 1, the lines in the script to be echoed to stderr before they are executed.. The optional left argument X specifies a character scalar of vector that prefixes each line of output. If X is omitted, the default is '+'.

If Y is 2, the effect is as if ⎕TRACE was set for every line of every function in the script. In this case the left argument (if any) is ignored.

If Y is 3, it specifies a combination of the above.

The result R is the previous value of the debug options.