/usr/share/perl5/Mail/SRS/Reversable.pm is in libmail-srs-perl 0.31-5.
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 | package Mail::SRS::Reversable;
use Carp qw(croak);
croak
"Please use Mail::SRS::Reversible instead of Mail::SRS::Reversable";
1;
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