You could slurp the whole file into a variable like this

use warnings;
use strict;

  my $filename//=$ARGV[0]; # i.e script.pl path_to_file
  my $data;

  open my $fh,'<',$filename or die"can't open file:$!";
  $data=do{local $/; <$fh>};  ## slurp the whole file once
  close $fh;

   my @guesses=();
   my $wrong=0;
   my @words=split/\s+?/,$data;
   my $choice=$words[rand @words];
   ....... # rest of the program
[download]

hope this helps