Don't worry too much about this. A lot of people haven't internalized the correct rule (use "an" before a vowel sound, not a vowel letter), and instead just use "an" before a vowel, regardless of the sound it makes. I've certainly never heard anything but /'jæm.ḷ/ in the wild.

You still wouldn't say "an why", as "w" isn't a vowel. If Anything, I can understand "an yamel" as more legitimate (as "y" is at least sort of a vowel).

No, "an YAML" is grammatically incorrect [0]. It's "a YAML".

What's more annoying: the odd (and wrong) belief that "An green apple" is grammatically correct. [1]

[0] http://english.stackexchange.com/questions/1016/do-you-use-a...

[1] http://english.stackexchange.com/questions/152/when-should-i...

I didn't say that "an YAML" is correct; I was first correcting that "an YAML" would be correct if it were "an why aih ahm ell" (it wouldn't), and then went further into "if anything" land saying that "an yahmell" is at least something I can bring myself to say without feeling sick inside. ;P

Counterpoint: this post [1] on HN front page at the moment contains the sentence "Never heard of a yml file?"

[1] http://www.crowdhoster.com/

FWIW, the Wikipedia article http://en.wikipedia.org/wiki/YAML corroborates the first pronouncation.