In the room of a prosodially long vowel (with the exception of ṛ) though it may not stand at the end, there is substituted a pluta for one at a time, under the above circumstances -- pratyabhivādeśūdre [[8.2.83]] & dūrāddhūte ca [[8.2.84]], in the opinion of Eastern Grammarians.,
This sutra indicates a special sthanin for the pluta vowel taught by 8.2.83 to 8.2.84. With the exception of ऋ, for every heavy vowel, though it may not be the final vowel of the vocative word, and for the final vowel also, but only one at a time, there is pluta substitution, in the opinion of Eastern Grammarians. Thus हे दे꣡३वदत्त or देवद꣡३त्त or देवदत्त꣡ ३ ॥ Similarly with य꣡३ज्ञदत्त, यज्ञद꣡३त्त or यज्ञदत्त꣡ ३ ॥
Why do we say गुरोः \of a prosodially long vowel\? So that the अ of य and ज्ञ in Devadatta and Yajnadatta may not be prolated, for this अ is short.
Why do we say अनृतः \with the exception of ऋ\? Observe कृष्णमि꣡३त्र, कृष्णमित्र꣡ ३, but never कृ꣡३ष्णमित्र ॥
The word एकैकस्य shows that the prolation should not be simultaneous, but of one at a time; not दे३वद३त्त३ ॥
The word प्राचाम् \in the opinion of Eastern Grammarians\ is used for the sake of creating option. So in one alternative, there is no prolation at all.
As आयुष्मान् एधि देवदत्त ॥ Thus the present sutra, makes 8.2.83 and 8.2.84, optional sutras. This also is an authority for the following dictum of Patanjali\सर्व एव प्लुतः साहसमनिच्छता विभाषा कर्त्तव्यः\ (Mahabhashya 8.2.92 Commentary). Thus all rules relating to Prolation become optional. In short, the word प्राचाम् should be read in all rules regarding prolation, and thus without doing violence (sahasa) to grammatical authority, one may have optional pluta everywhere.,