Pāṇini sūtras

Guṇa is substituted before a sârvadhâtuka and an ârdbadhâtuka affix, for the ik vowels of the Causative stems which take the augment p (VII.3.36), and for the short penultimate vowel of a root which ends in a single consonant.

1. puk+anta+laghu+upadhasyaपुक्+अन्त+लघु+उपधस्य

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   pप्	pukपुक्	pukपुक्	pukपुक्	pukपुक्
   aअ	antaअन्त	antaअन्त	last syllable	antअन्त् + plus aअ
   lल्	laghuलघु	laghuलघु	short	laghलघ् + plus uउ
   uउ	upadhāउपधा	upadhasyaउपधस्य	penult	upadhउपध् + plus asyaअस्य

2. caच

   Part	Lexeme	Sandhi form	Meaning	Stem
   cच्	caच	caच	besides	caच

Anuvṛtti

1. guṇaḥगुणः 7·3·82

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   gग्	guṇaगुण	guṇaḥगुणः	guṇaगुण	guṇगुण् + plus aḥअः

2. sārvadhātuka+ārdhadhātukayoḥसार्वधातुक+आर्धधातुकयोः 7·3·84

   Part	Lexeme	Sandhi form	Meaning	Stem + termination
   sस्	sārvadhātuसार्वधातु	sārvadhātukaसार्वधातुक	sārvadhātukaसार्वधातुक	sārvadhātukसार्वधातुक् + plus aअ
   āआ	ārdhadhātuआर्धधातु	ārdhadhātukayoḥआर्धधातुकयोः	ārdhadhātukaआर्धधातुक	ārdhadhātukआर्धधातुक् + plus ayoḥअयोः