/usr/share/perl5/Mail/Message/Field/ is in libmail-box-perl 2.099-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/perl5/Mail/Message/Field/AddrGroup.pm
/usr/share/perl5/Mail/Message/Field/AddrGroup.pod
/usr/share/perl5/Mail/Message/Field/Address.pm
/usr/share/perl5/Mail/Message/Field/Address.pod
/usr/share/perl5/Mail/Message/Field/Addresses.pm
/usr/share/perl5/Mail/Message/Field/Addresses.pod
/usr/share/perl5/Mail/Message/Field/Attribute.pm
/usr/share/perl5/Mail/Message/Field/Attribute.pod
/usr/share/perl5/Mail/Message/Field/Date.pm
/usr/share/perl5/Mail/Message/Field/Date.pod
/usr/share/perl5/Mail/Message/Field/Fast.pm
/usr/share/perl5/Mail/Message/Field/Fast.pod
/usr/share/perl5/Mail/Message/Field/Flex.pm
/usr/share/perl5/Mail/Message/Field/Flex.pod
/usr/share/perl5/Mail/Message/Field/Full.pm
/usr/share/perl5/Mail/Message/Field/Full.pod
/usr/share/perl5/Mail/Message/Field/Structured.pm
/usr/share/perl5/Mail/Message/Field/Structured.pod
/usr/share/perl5/Mail/Message/Field/URIs.pm
/usr/share/perl5/Mail/Message/Field/URIs.pod
/usr/share/perl5/Mail/Message/Field/Unstructured.pm
/usr/share/perl5/Mail/Message/Field/Unstructured.pod