exten => gemara,1,Read(masech|what-masech|3|||3)
exten => gemara,n,Gosub(masech-check,1)
exten => gemara,n,Gotoif($[${ISNULL(${masech})}]?gemara|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,Set(${ISNULL(${masech})})
exten => masech-check,n,Return