Well, there's the analogLib switch element which, if SW was
a node voltage, would do what you want. Not the form you
ask for, but the result. And it wouldn't look for strict equality,
but >= the threshold parameter.
You could stack switches, like relay logic, to get closer to
an = function (arbitrarily so, but finite slop).
You can either type this directly into the CIW, or define it as a SKILL function or procedure.
For more info, get sklangref.pdf (find it in $CDS_INST_DIR/doc/sklangref/sklangref.pdf or via G00GLE). Therein, search for examples by the search word else.
The Spectre simulator's OCEAN language should use a similar syntax.
See the Spectre® Circuit Simulator Reference or the Virtuoso® Simulator Measurement Description Language User Guide and Reference somewhere in the $CDS_INST_DIR/doc/ libs.