Helpful reading–

• Plack::Builder
• Plack::Middleware
• Plack::App::URLMap
• Plack::Middleware::Conditional
• plackup
• Plack::Middleware::Session and PSGI—might help unify apps by, e.g., sharing sessions via psgix.session.

# If you're not reasonably up to date-
sudo cpanm Plack Catalyst Catalyst::Devel
[download]

Full steps for testing two Cat apps in one server

# *nix centric.
mkdir cattest
cd cattest
catalyst.pl OneFish
catalyst.pl TwoFish
vi^W
emacs a-one-an-a-two-a.psgi
# But I keed!
[download]

a-one-an-a-two-a.psgi

#!/usr/bin/env perl
use strict;
use Plack::Builder;
use FindBin;
use lib "$FindBin::Bin/OneFish/lib",
    "$FindBin::Bin/TwoFish/lib";
use OneFish;
use TwoFish;

my $app = builder {
    mount "/two" => TwoFish->psgi_app(@_);
    mount "/" => OneFish->psgi_app(@_);
    # Root needs to be last or it'll eat others.
};
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Run, dog, run

env CATALYST_DEBUG=0 plackup a-one-an-a-two-a.psgi
HTTP::Server::PSGI: Accepting connections at http://0:5000/
[download]

Visit http://localhost:5000/ (or whatever name/ip your box prefers) and http://localhost:5000/two/ and don't forget to tip your servers.

Caveat: this might lead to entangling or making cross-dependent coding choices which would be bad. Make an effort to keep things compartimental. Abstract and separate commonality like sessions/auth. If each app can't run alone after you're done, you might as well have rolled them all into one to start.