[
if [* < says < any < Xs < here]
and [i < am < a < X]
and [X < is < the < singular < of < Xs]
say [! < i < am < a < X]
]

[
if   [Xs < is < the < plural < of < X]
then [X < is < the < singular < of < Xs]
]

[
if   [Xs = concat(X, "s")]
then [Xs < is < the < plural < of < X]
]