eq1:=x^2-x*cos(y)-x1:x1 may be considered as a parameter while x, y are the unknowns. Each line of the parameter file indicates a name of a parameter and its value. Thus
x1 1is a valid parameter file. Then you may use the programs of the MAPLE library (see section 12.3) to generate the parser files for the solver: these programs enable to specify that x1 is not an unknown. The generated files will contain the parameter x1 and if you want to solve a particular occurrence of the parametric system you just have to add an argument to the command line of the generic solver:
-P [parameter file]and if you want to study another occurrence (for example when the value of x1 is 2) you just have to change the value in the parameter file.
Some specific parameters with special names may also be used to speed up the computation, see section 220.127.116.11.