Hmmm...it is not obvious according to the pod but there is a method in the code that looks like it does this, set_seq. The comment at the head of the code reads:

# Set an escape sequence/function combo for a read handle for intercon
+nect.
  # Ex: $read_handle->set_seq('',\&function,\@parameters);
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I found this after noticing that the interact appears to be looping over some structure. You can set debugging on in the following way. It might help:

use Expect;

$Expect::Log_Stdout=1;
$Expect::Debug=3;
$Expect::Exp_Internal=1;

...
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