What you are trying to do of "anticipating the input" cannot be done, with the value being editable on the command-line.

Very strong words, considering the shell does it all the time.

There may not be a module to do this (and I am not fully convinced of this), but it most definitely can be done. At the very worst, you would need to push the prefill onto the line, and process the backspaces / ^H yourself.

Update: See Term::ReadKey as a very possible tool to use to implement this, and Re: <STDIN> "anticipate" input? points to Term::ReadLine, which also looks like it could work (see addhistory as a possible method to do this).