In the reduplicative syllable, a prosodially short vowel is lengthened in the reduplicated Aorist of the Causative when the vowel of the root is light and the root has not lost its end-vowel before the Causative ṇi,
Thus अचीकरत्, the इ 7.4.79 is lengthened. Similarly अजीहरत्, अलीलवत्, अपीपवत् ॥ Why do we say which is prosodially light? Observe अबिभ्रजत् ॥ Why do we say when the vowel of the root is light? Observe अततक्षत्, अररक्षत् ॥ Why do we say in the reduplicated Aorist? Observe अहं पपच ॥ The word पर is understood here also, so the rule will not apply to simple roots as अचकमत् ॥ The words 'anaglope' are to be read here, therefore not so in अचकथत् ॥,