binding.pry appears to be debouncing and then re-displaying text input

I'm following along with a tutorial book, and in order to step through my code I've required pry and added a binding.pry reference in a method which gets executed:

require 'pry'

module Rulers
  module Model
    class FileModel
      def initialize(filename)
        @filename = filename
        binding.pry
        basename = File.split(filename)[-1]
...

When I load the code which executes this constructor method, I successfully hit my binding.pry debugger point as expected. However, when I start typing commands at the prompt, the characters I enter are printed out in the same prompt:

[7] pry(#<Rulers::Model::FileModel>)> .whic.whichh

In the above example, I typed .which. I had gotten all the way to .whic when the REPL added the characters I had typed thus far (i.e. it added .whic to .whic, resulting in .whic.whic). The last character I typed was h, which registers after .whic.whic. Finally, the last h I typed was also appended to the chars on the prompt.

Interestingly, the duplicated chars do not appear to affect the REPL's ability to understand the commands I type in. For example, the following:

[8] pry(#<Rulers::Model::FileModel>)> .which .which vim
[8] pry(#<Rulers::Model::FileModel>)> .which vim
/usr/bin/vim

In the above example, I was successful in typing .which quickly enough to not result in a muddled version of the which command, and I also pressed Enter before vim could be duplicated erroneously. If the redundant 2nd .which command were to affect my ability to return the expected output, I would expect to see an error returned. Instead, I see /usr/bin/vim as I would expect when typing which vim in my regular, non-pry command line prompt.

I have no theories on where to begin debugging this. Any ideas?