Man pages matching name pdl::io::fits in section 3pm:

PDL::IO::FITS.3pm.en	debian 10 / pdl
PDL::IO::FITS.3pm.en	debian 11 / pdl
PDL::IO::FITS.3pm.en	debian 12 / pdl
PDL::IO::FITS.3pm.en	debian 13 / pdl