  The interest in the description of the properties of fluids of restricted
dimensionality is growing for theoretical and practical reasons. In this work,
we have firstly developed an analytical expression for the Helmholtz free
energy of the two-dimensional square-well fluid in the Barker--Henderson
framework. This equation of state is based on an approximate analytical radial
distribution function for $d$-dimensional hard-sphere fluids ($1\leq d\leq 3$)
and is validated against existing and new simulation results. The so-obtained
equation of state is implemented in a discrete perturbation theory able to
account for general potential shapes. The prototypical Lennard-Jones and Yukawa
fluids are tested in its two-dimensional version against available and new
simulation data with semi-quantitative agreement.
