exten => s,n,Read(subject|what-sub|3|||3)
exten => s,n,Gotoif($[${subject}=1]?gemara:mishna)
exten => gemara,1,Read(masech|what-masech|3|||3)
exten => gemara,n,Gosub(masech-check,1)
exten => gemara,n,Read(daf|what-daf|3|||3|)

.
.
.

exten => masech-check,1,Noop(Check to see if masech exists)
exten => masech-check,n,Gosubif($[${masech}=>28])?

exten => masech-check,n,Return