So, undef before I return or check it for definedness before I fill it?

Update: I emptied the two keys before I returned, and it seems to work.

sub random {
  my ($user_input, $list) = @_;
  
  $list->{'all'}  = [ map { @$_ } values %{$list} ];
  $list->{'keys'} = [ grep {$_ !~ /(?:all|keys)/} keys %{$list} ];
  
  my $random_thing;
  if ($user_input && $user_input =~ /(?:help|options)/) {
    $random_thing = 'Your options are: '.join(', ',sort @{$$list{'keys
+'}}).', or all.';
  }
  elsif ($user_input && $user_input =~ /dump/) {
    use Data::Dumper;
    $random_thing = Dumper($list);
  }
  else {
    my $input = $user_input ? $user_input : 'all';
    my @random_list = shuffle(@{$$list{$input}});
    $random_thing = $random_list[rand @random_list];
  }
  
  $list->{'all'} = [];
  $list->{'keys'} = [];
  
  return $random_thing;
}
[download]

That's one way to do it. Or you could just delete the keys you don't want (re)included before you (re)populate them:

sub random {
   my ($user_input, $list) = @_;
  
   delete $list->{all}; delete $list->{keys};

   $list->{'all'}  = [ map { @$_ } values %{$list} ];
   $list->{'keys'} = [ grep {$_ !~ /(?:all|keys)/} keys %{$list} ];
[download]

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

I thought about using delete, however the doc suggested emptying the lists would be faster. If so I would prefer speed since I may be using these many times (100s of times even) in a script.

No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
Lady Aleena

Why not leave %list as is ?

sub random {
  my ($user_input, $list) = @_;
  
  if ($user_input =~ /(?:help|options)/) { 
     my $keys =  join ", ",keys %$list;
     return "Your options are: $keys, or all.";
  }
  elsif ($user_input eq 'dump') {
    use Data::Dumper;
    return Dumper($list);
  }
  else {
    my @values=();
    if ($user_input eq 'all'){
      @values = map { @$_ } values %$list;
    } else {
      @values = values @$list{$user_input};
    }
    return (shuffle @values)[0];
  }    
}
[download]

poj

poj, I did it your way (with my own additions) by not creating two new hash keys.

use List::Util qw(shuffle);

sub random {
  my ($user_input, $list) = @_;
  
  my $random_thing;

  if ($user_input && $user_input =~ /(?:help|options)/) {
    my $keys = join(', ', keys %{$list});
    $random_thing = "Your options are: $keys, or all.";
  }

  elsif ($user_input && $user_input eq 'list') {
    $random_thing = $list;
  }

  else {
    my @random_list;

    # The following gets the keys to randomize instead of $list->{'key
+s'}.
    if ($user_input && $user_input eq 'keys') {
      @random_list = keys %{$list};
    }

    # The following gets the entire list to randomize instead of $list
+->{'all'}.
    elsif (!$user_input || $user_input eq 'all' ) {
      @random_list = map { @$_ } values %{$list};
    }

    else {
      @random_list = shuffle(@{$$list{$user_input}});
    }

    $random_thing = $random_list[rand @random_list];
  }
  
  return $random_thing;
}
[download]

No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
Lady Aleena

poj, can you accept I didn't think about doing it your way? Also, you don't have keys available to random generate nor did you make 'all' the default if no $user_input. I sometimes want a more general result which is why I have a keys list. I will give this a big think and maybe incorporate some of this. Thanks!

No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
Lady Aleena