Here is another workaround, more practical and more down-to-earth:

In your project's dir I assume you have lib/ with all your mojo code. Create dirs lib/Mojo and lib/Mojo/resources . Copy original Mojo::Util in lib/Mojo/Util.pm . In my linux box I can do whichpm Mojo::Util and get /usr/local/share/perl5/5.32/Mojo/Util.pm (to install whichpm do cpanm -f App::whichpm). Copy /usr/local/share/perl5/5.32/Mojo/resources/html_entities.txt into lib/Mojo/resources/html_entities.txt and edit according to your needs. This will be what Mojo::Util will use as its html_entities.txt. That's the first part.

The second part is to modify your mojo-app script so that it looks for packages FIRST in your lib/ dir before anywhere else including the Mojolicious installation location. Mine looks like this:

#!/usr/bin/env perl

use strict;
use warnings;

our $VERSION = '0.01';

#ADD THIS before loading anything else
#adjust catdir so that it finds 'lib' from where THIS script resides
#mine is scripts/hero that's why I have the '..'
use FindBin;
use File::Spec;
use lib File::Spec->catdir($FindBin::Bin, '..', 'lib');
# or just use lib a constant path to avoid loading extra packages
#####

use Mojo::File qw(curfile);
use Mojolicious::Commands;

# Start command line interface for application
Mojolicious::Commands->start_app('Hero');
[download]

The caveat is that your local Mojo::Util will not be updated when Mojolicious gets an update. But there are workarounds for this too, I am sure.

bw, bliako