• my $r = \{expr};
  [download]

  is the same thing as

  my @rv = expr;
  my %h = @rv;
  my $hr = \%h;
  my $r = \$hr;
  [download]

  There's no coderef anywhere in there. That sets the value at key firstTask to a reference to a reference to a hash which was initialized with the result of prepare.

• Furthermore,

  $ThingsToDo{firstTask};
  [download]

  is a no-op. Even if $ThingsToDo{firstTask} returned a code reference, there's nothing to cause the referenced code to get executed. To execute the code referenced by $ThingsToDo{firstTask}, use

  &{$ThingsToDo{firstTask}}();
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  or better yet,

  $ThingsToDo{firstTask}->();
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• Finally, $project needs to be variable. It needs to be an argument.

I think you meant

my %ThingsToDo = (
   firstTask => sub { my $pkg = shift; $pkg->prepare(@_) },
);

...

$ThingsToDo{firstTask}->($project);
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But that's much more complex than required, and would involve lots of redundancy (sub { my $pkg = shift; $pkg->XXX(@_) }.