This is 'the plaint of a 'Mallu''
English appears to have a range of long ('deergha') vowel prononciations from 'ah' (as in 'card') to 'oh' (as in 'court'). The obvious intermediate vowel sound is 'aw' as in 'broad'. There seem to be further subtleties at the 'oh' end of the above 'spectrum' with 'code', 'pour, and 'toad' all *probably* having slightly different vowel sounds in 'Queen's (?)' English (we wont worry about these rather extreme subtleties here).
All Indian languages, on the other hand, basically have only the two extreme sounds from this range - the 'card' and 'court' ones. Anything in the middle and finer distinctions of the code-court variety are not part of their phonetics (the 'oo' sound of say 'boot' is there in Indian languages but here we look at only about the above-mentioned spectrum of vowel sounds and 'boot' lies beyond that).
The distinction between the 'aw' and 'oh' in English pronunciation is very subtly inconsistent - 'road' and 'broad' have very different vowel sounds and so have 'toll' and 'doll'. And there is no obvious rule or pattern. This should really have created massive confusion to most Indians who learn the intricacies of English pronunciation as an add-on to the sound structure of their respective mother tongues - they basically lack the 'aw' sound of 'broad' and even after adding this sound to their 'phonetic repertoire', one has to learn where to employ it - as distinct from the 'road' sound. But, almost incredibly, the huge majority of Indian learners of English are seldom troubled by this and almost invariably get things right!
...Except, of course, those who grew up with Malayalam! In some very typical cases, one can have a 'Mallu' named 'Tom' say his own name as 'Tome' (rhyming with 'dome'), 'Tony' and 'tawny' having identical pronunciations and a quite decent school student getting confused whether 'coat' (articulated, not written) was an object to be put on or to be slept on. It is not that Mallus do not know the 'aw' sound of 'broad' - they do know it exists and do pronounce it, but they employ it arbitrarily in confusion with the 'road' sound.
Indeed, what really puzzles me is how the rest of India gets it right almost always although they do not start off with any phonetic advantage over Malayalis. A typical Mallu can take several years to get over this severe confusion; many never make the cut and some truly blessed souls never even know they are messing up!
Well, one might say Tamil speakers say the open 'ah' for the 'aw' - but they never are CONFUSED. They would say 'saart' for 'sort' (almost like an American would put it, so it is cool!) but they will not pronounce 'port' as 'part' or 'fort' as .... To be more precise, although the hard-core 'Tam' makes only the two extreme sounds, - 'ah' as in 'part' and 'oh' as in 'court' - he knows, with uncanny precision, which words have an 'aw' ('broad') sound and pulls them back to 'ah's; those with 'oh'('court') sounds are pronounced as such - no trace of the 'coat vs cot' confusion.
On the other hand, the hapless Mallu (poor soul, even 'Goad' is indifferent to his plight) would conjure up spurious rhymes and miss the real ones. Unlike the Tam, he uses the 'aw' ('broad') sound in addition to the 'extreme' sounds; and uses it indiscriminately to create havoc - pronouncing 'code' as 'cod' and coke' as, well, one can go on and on... Get a Mallu to 'roam in Rome' and he will get lost, although he might very well enjoy 'Pope music'!. ..!
I conclude with this assertion, it simply ain't fair: why do ONLY Mallus have to suffer so much from this deeply devious feature of English??
Note added on May 30th-05:
1. Here is a link on the so-called 'cot-caught merger'
; amazing that in 'proper' English, 'cot' and 'caught' actually have different and distinguishable pronunciations! This also suggests a technical name for the Mallu's confusion: the 'cot-coat merger'.
2. The Malayali is not entirely alone in his confusion. It has been brought to my attention that some North Indians, especially Gujaratis make the 'road-broad' mess.
3. Further, the assertion that no Indian is basically equipped with the 'broad' vowel is not entirely accurate; Modern Hindi-Urdu has a somewhat similar sound in 'koun' (who). This is almost certainly a distortion from the original sanskrit pronunciation which would have been like 'kown' (same as in 'owl').
Update (July 2016): There is a huge ongoing confusion among Keralan netizens as to whether 'trolling' is a usually nasty cyber activity or a sometimes controversial maritime one. The reason, of course, is 'trawling', performed by mechanized fishing craft (it eats into the catch of more traditional fishermen). There are 4 distinct ways to pronounce the 'troll'-'trawl' pair - to make both 'trawl', to make both 'troll', to get both words right and to get both wrong. My informed guess is that a survey among Mallus will yield the first 3 possibilities with roughly equal frequency and the last with slightly less but considerable frequency. This guess would, of course, imply that the clear majority of respondents would pronounce both words just the same(Note: Intriguingly, even 'trolling' has maritime connotations - it literally means to fish with a hook and line)!