thirithanthAgilum dhEva pirAnudaik
kariyakOlath thiruvuruk kANban nAn
periyavaN kurugUr nambikku
AL uriyanAy adiyEn peRRa nanmaiyE

Meaning:

thirithanthAgilum 		- Were I to leave Nammazhvar and return 
nAn kANban 			- I would see and worship 
dhEva pirAnudai 		- the Lord of the nithyasUris 
kariya 				- whose form is dark
kOlam 				- and delightful. 
adiyEn peRRa nanmaiyE 		- This great gain was obtained by me 
uriya AL Ay 			- due to the fact that I surrendered and belonged to
periyavaN kurugUr nambikku 	- Nammazhvar of the great Kurugur.

Vyakhyana Saram:
Madhurakavi Azhvar is talking about the Lord in this pasuram as Nammazhvar is attached to Him. In the previous pasuram, he had said that he knows no other lord other than Nammazhvar; however, as Nammazhvar has great attachment to Him, he also sings about Him. Even though he has not chosen the path that leads to Him directly, since He is in the path that was chosen by Madhurakavi Azhvar (to his acharya), he gets attached to Him. It is not that he has to let go of Him as He is in an unsuitable path to the higher goal. Since He is present in the great path that leads to an acharya, Madhurakavi Azhvar will not let go of Him. Madhurakavi Azhvar is attached to anything to which his acharya attached.

thirithanthAgilum:
Thirikai here means to return. That is, returning along the path in which he reached his acharya Nammazhvar. There is no returning after reaching Him ("na ca punarAvartate"). Keeping Him as the first step if one were to go ahead then upon returning one would simply come back to Him. Such a great result has happened to Madhurakavi Azhvar because he has surrendered at the lotus feet of Nammazhvar.

dheVa pirAnudai kariya kOlath thiruvuru:
Were he to lose his bearing and return, he would come to the where the nithyasUris exist. And there he would see the divine and beautiful dark form of the Lord of the nithyasUris ("kOlamE thAmaraik kaNNathOr anjana nIlamE").

dhEva pirAnudaik kariya kOlath thiruvuruk kANban nAn:
That which he has chosen not to pursue is that beauty and divinity that is seen only by the nithyasUris. Even though he has not chosen that as his goal, it is the goal of his goal (that is, Nammazhvar's goal is the Lord).
His beauty is beyond everything such that it is impossible to neither comprehend it in one's mind ("jyotImshyAdityadvad rAjan kurUn pracchAdayan sriyA") nor see it with one's eyes ("tharunau rUpasampannau"). Madhurakavi Azhvar sees such a beauty due to his acharya's grace.

kANban:
Just as a person who was deeply into the bhakti yoga sees the things of this world when he gives up on his yoga, so too Madhurakavi Azhvar sees Him when he leaves his acharya and returns.

periyavaN kurugUr:
He gave the knowledge to see Him, to Nammazhvar alone. However, Nammazhvar gave that knowledge to everyone. Having given such an acharya to this world, Kurukoor has great fame and importance. It is also important because many acharyas are present there. Nammazhvar also refers to himself in Thiruvaymozhi as "periyavaN kurukUr sadakOpan".

nambi:
Nammazhvar also is a pUrna because he is the leader of such a city.

periyavaN kurgUr nambi:
Is Nammazhvar's completeness only such that one can just say Madhurakavi Azhvar gave up something and is attached to something? What Madhurakavi Azhvar gave up and what he attached himself to speaks volumes about the greatness of Nammazhvar's pUrnathvam.

AL uriyanAy:
Madhurakavi Azhvar says that he is a devotee that belongs to Nammazhvar in the sense that he is not attached to one thing and his acharya is attached to something else; he is attached to the exact same thing that his acharya is.

adiyEn:
He has become Nammazhvar's devotee due to his acharya's simplicity and approachability.

adiyEn peRRa nanmaiyE:
Madhurakavi Azhvar sees as the height of service by being attached to that which is pleasing to his acharya.

peRRa nanmaiyE:
He will not consider as bad that which is of great importance to his acharya. Instead he will be attached to the same. Therefore, he says that he has gained a great thing.