vanishing output with expect_out(buffer)

Question

Used language: TCL / Expect

When I print the output of the expect_out(buffer), it removes the whole printed line for some kind of reason. I have no clue on what is doing this. I've even broken down the "puts" output with -nonewline to be sure and this output also vanished for this line.

Code:

     set var $expect_out(0,string)
     foreach line [split $var \n] {
         puts -nonewline "line: "
         puts $line
     }

output:

    somedata
    line: somemoredata
    line: evensomemoredata

expected output:

    line: somedata
    line: somemoredata
    line: evensomemoredata

What can cause this output? How can I even troubleshoot this?

*Edit after answer:

To help others with this problem in Expect, it helps to add the following command in your expect script to troubleshoot:

    exp_internal 1

This shows everything that is going on, including the values in the buffer that were returned.

Answer 1

Usually in Expect, \n chars in the spawned program's output will be converted to \r\n. You can manually remove the \r chars like this:

set var $expect_out(0,string)
set var [regsub -all "\r" $var ""]
... ...