Re: Looking for pointers or optimizations.

[aitap]

In addition to the previous comments,

my $words_file = @ARGV;

You assign an array to a scalar. Array is treated in scalar context, and you have only number of arguments in it. Use this instead: my ($words_file) = @ARGV;. In this case an anonymous array gets assigned, and nobody gets harmed.

open (my $fh, ">", $words_file);
my @words;
while (<>) {
    push(@words, $_);
}

You read STDIN, not the $fh. Use <$fh>, not just <>. Also, in array context the <> operator returns the array with file contents. You can just run my @words = <$fh>;. See readline for more.

my $word = lc($words[rand($words) + 1]);

scalar @words returns count of the words; rand returns any number between (including) 0 and specified number (not including). You should also round this value using int: my $word = lc $words[int rand($words+1)];

_{Edit: my @words = <$fh>; # not $fh}