Moose is a postmodern object system for Perl5. Moose is wonderful.

Unfortunately, Moose has a compile-time penalty. Though significant progress
has been made over the years, the compile time penalty is a non-starter for
some very specific applications. If you are writing a command-line application
or CGI script where startup time is essential, you may not be able to use Moose
(we recommend that you instead use persistent Perl executing environments like
FastCGI for the latter, if possible).

Mouse is a Moose compatible object system, which aims to alleviate this penalty
by providing a subset of Moose's functionality.

WWW: https://metacpan.org/pod/Mouse