/usr/share/perl5/Mojolicious/public/mojo/prettify/lang-mumps.js is in libmojolicious-perl 5.54+dfsg-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/perl5/Mojolicious/public/mojo/prettify/../../../../../javascript/prettify/lang-mumps.js