A varnam is one of the hardest phase of the learning process in the shishya-parampara (student learning process) within the Karnatic classical school, a grounding in fundamentals of sorts. In my opinion, that intricacy makes them more soulful and complete as compared to. say, a kriti.

Varnam's are further classified into "pada" varnam and "ata-tala" varnams.  "Viriboni" is one such Ata-tala varnam set to Bhairavi ragam by Pacchimirium Sri Adiyappaiyer

Composition: Viriboni
Composer: Pacchimiriyam Adiyappa
Raga:  Bhairavi                 
Mela: Natabhairavi - 20

Type:  Varnam                  
Tala :  Khandajathi Ata

Arohana:    S G1 R2 G1 M1 P D2 N1 S || S Gi Ri Gi Ma Pa Dhi Ni S
Avarohana:S N1 D1 P M1 G1 R2 S      || S Ni Dha Pa Ma Gi Ri S
Bhashanga Raga: Chatusruti dhaivata


PALLAVI:
viribōṇi ninnē kōri ||
marulu konnadi-rā ||

ANUPALLAVI:
sarasuḍau dakṣiṇa dwāraka ||
sāmi śrī rājagōpāla dēva ||

CHARANAM:
chirunavvu mōmuna ||


If you are thinking this is just five lines, dont. Ata-tala varanams are very complex pada-varnams and we usually take 25 minutes to finish it. Yeah 25 minutes to practise five lines of lyrics!

Ata-tala varnam, as the name suggests, are set to a 14-beat cycle, far different as compared to a varnam set to Adi tala. That complexity in beats makes it complex and yet soulful, thanks to the complex svara structures.

They are also used for the Bharatnatyam dance recitals, where the ragam-tanam-pallavi is more intricate as compared to a regular varnam and it could go on for as long as 35-45 minutes, depending on the choreography and the visual story-telling the artiste-dancer indulges in.