Title: Substitution of function with module name by variable
Goal: Merge all instances of the expression `math:sin(X)'.
Parameters:
    [   {file,"ref_emath.erl"},
        {posrange,{81,91}},
        {varname,"Sin"} ].
Documentation:
 The expression can be substituted,
 because `math:sin/1' is a function without side effects.
 Note, however, that the applications of `io:format/2'
 would not be eligible for merging,
 as printing to the screen is a side effect.
Status:unsupported.
