@true translation of the pandaspanker sUtra

The pandaspanker sUtra ACTUALLY translates to —

Before all consonants except r र् z श् S ष् s स् h ह्, replace /M with a nasalized /savarNa of the consonant. (This is the true version of the rule.)

The translation that I gave in page anusvArasy... is fake, but please make your students learn THAT one anyway, not the true one here. Why? Because this is one of the points where current usage is at odds with PC Sanskrit.

The differences are —

(1) According to pandaspanker, you may optionally replace padafinal /M with y~ v~ l~ before y v l respectively. In my experience (based on what I heard around), few people ever use the y~ v~ l~ nowadays — /M always stays M before y v l .

(2) According to rule vApadAntasya, when the m is padafinal you may optionally NOT do the replacing and pronounce the /M in its proper form, a hum. In my experience, nowadays the replacing is all but compulsory; few people ever say a hum in those positions.

The /yay in anusvArasy... makes the replacement happen before all consonants except the /zal. So we must replace M with r~ before another r , isn't it so?

You are right, /pANini says so. Yet commentarists agree that this replacement of M never happens and the M stays M . They also agree that there is no such thing as r~ in Sanskrit.

Why didn't /pANini mention that M stays before r ? He either forgot, or figured out that students were smart enought to work out that if it were enabled, then catastrophe would ensue —

/sam + rabdha-
→ sar~rabdha- by replacing /M
→ sarabdha- by rori
→ sArabdha- by DhralopepUrv...

And that is clearly undesired — !**saMrabdha- is very obviously the right form.