You need to clear the input buffer before reading the next response.
Maybe this module does already cover all your requirements? IO::Prompter or Term:UI

Update: The following method clears the input buffer (at least on Unix):

use Term::ReadKey;

sub flush_stdin {
  ReadMode 4;
  ReadLine(-1);
  ReadMode 0;
}

sleep 5;      # type 'something'

flush_stdin();
$|=1; 
print "---> ";
chomp (my $answ = <STDIN>);
print "answ: ($answ)\n";    # w/o 'something'
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Update: Cannot test it under Windows, but maybe Win32::Console works (see Flush() method)?