The minimal working CLI

My-Modules-Script.pm6

#!/usr/bin/env perl6

## To get a MAIN to run in a unit module/package:

unit module My-Modules-Script;

## You must have the `is export` here; `our` will not work

sub MAIN($x) is export {
    say "This is the module's MAIN called with $x";
}

## And you must call it differently:

# $ ./My-Modules-Script.pm6
# $ ./My-Modules-Script.pm6 22
# $ perl6 -M My-Modules-Script -e ''
# Usage:
#   -e '...' <x>
# $ perl6 -M My-Modules-Script -e '' 42
# This is the module's MAIN called with 42