interface_build {
    {s.perturb} 0
    {Randomly perturb eastings and northings of sites.}
    {entry input {Input sites list:} 0 sites}
    {entry output {Output perturbed sites list:} 0 sites}
    {checkbox distribution {Uniform distribution of E/N perturbations.} "" uniform}
    {checkbox distribution {Normal distribution of E/N perturbations.} "" normal}
    {entry parameters {Input maximum (for uniform dist.) or mean and stand. dev. (for normal dist.):} 0 ""}
    {checkbox -q {Run quietly.} "" -q}
}