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)  ;sanity check
exten => gemara,n,Read(daf|what-daf|3|||3|)   ; HERE i would like another sanity sheck using the same sub
exten => gemara,n,ControlPlayback(custom/${LANGUAGE}/${masech}/${daf}|30000|3|1|0|5|8|j)

.
.
.

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

exten => masech-check,n,Return