/usr/share/doc/libclass-insideout-perl/examples/ReadOnly.pm is in libclass-insideout-perl 1.13-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | package t::Object::ReadOnly;
use Class::InsideOut qw/readonly new/;
readonly name => my %name;
readonly age => my %age;
1;
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