  We present a numerical implementation for the solution of the relativistic
radiation hydrodynamics and magnetohydrodynamics equations, designed as an
independent module within the freely available code PLUTO. The radiation
transfer equations are solved under the grey approximation and imposing the M1
closure, which allows the radiation transport to be handled in both the
free-streaming and diffusion limits. Equations are integrated following an
implicit-explicit scheme, where radiation-matter interaction terms are
integrated implicitly, whereas transport and all of the remaining source terms
are solved explicitly by means of the same Godunov-type solvers included in
PLUTO. Among these, we introduce a new Harten-van Leer-contact (HLLC) solver
for optically thin radiation transport. The code is suitable for
multidimensional computations in Cartesian, spherical and cylindrical
coordinates, using either a single processor or parallel architectures.
Adaptive grid computations are also made possible, by means of the CHOMBO
library. The algorithm performance is demonstrated through a series of
numerical benchmarks by investigating various different configurations with a
particular emphasis on the behavior of the solutions in the free-streaming and
diffusion limits.
