Could not find List::Util

I'm trying to compile some raku code I saw on https://replit.com/languages/raku. The code is from https://stackoverflow.com/questions/75354706/why-is-raku-reporting-two-terms-in-a-row-when-i-define-a-new-operator.

It begins like this:

unit module Format;
use List::Util;
...

It fails to compile with:

 raku ./main.raku
===SORRY!=== Error while compiling /home/runner/l4gp3hvdnhd/./main.raku
Could not find List::Util in:
    inst#/home/runner/.raku
    inst#/opt/rakudo-pkg/share/perl6/site
    inst#/opt/rakudo-pkg/share/perl6/vendor
    inst#/opt/rakudo-pkg/share/perl6/core
    ap#
    nqp#
    perl5#
at /home/runner/l4gp3hvdnhd/./main.raku:3
exit status 1

On the other hand I see this is a valid module - https://raku.land/zef:lizmat/List::Util.

Why is it failing?

You do not have List::Util installed. Since you're using an online interpreter you will most likely have a lot of trouble doing this. Instead I recommend installing Raku on your local machine with rakubrew.

Then run the following commands:

rakubrew download # Will install latest raku and zef
zef install List::Util

Now you should be able to run your code on your local machine, and you'll have access to the List::Util library.

TL;DR Run zef install --/test List::Util in the console, put use lib '.'; at the top of your Raku main.raku, and run, don't walk, with your program, before gremlins gleefully render your efforts in vain. Or maybe just listen to Liz and Rawley.

As Liz and Rawley have noted, you need List::Util installed.

But while I largely agree with them in practice (it may be a pain to use replit to do what you're trying to do) I think a different response to complement theirs might be helpful.

One of the ways replit is trying to distinguish itself from other online evaluators, is that it is trying to be akin to a full dev environment.

In reality it's early days in their ambitious project, and beggars can't be choosers (if you're not paying, it's hard to complain if things don't work out as you might want), but of particular relevance for this SO it is worth noting that it does have console/shell facilities and they've installed Rakudo Star, or perhaps just something like it, including the Raku package manager pretty much everyone uses (zef).

Thus this command, which I just ran in replit's console of a new raku session, worked:

zef install --/test List::Util;

(The --/test tells zef not to run tests. I've only got a free account and it looked like replit killed zef's process when I ran just zef install List::Util during its running of tests. Presumably they take too long, but I don't know.)

And then this main.raku also worked:

use lib '.';              # Tell Raku(do) libs are in current directory.
use List::Util <notall>;  # Load and import `notall` from module.
say notall { 42 }, 99;    # Try it.

But now the rub. As I was composing this answer, the expected happened. My internet connection momentarily flaked out, the replit rebooted the session, and while my main.raku code was rescued, both List::Util and my console history had disappeared, so I had to paste the install command again and rerun it to get the module installed again.

It's all just throwaway container magic, and there's only so much replit has done thus far to make the simulation of a real full local dev environment really work.

Maybe if your Internet connection is rock solid and/or you're using a paid replit account and/or it's the full moon, it'll all work out. Or maybe you're best off following Rawley's advice.

Speaking of which (I mean Rawley's advice to set up your Raku dev environment locally), if you do install locally you can also install the awesome free version of CommaIDE.