As a 21 year old this is not ageism in the slightest, it is reality that as you see more and more problems the applicability of some solutions becomes more apparent. For example, when talking to seasoned engineers who have written a lot of concurrent code they immediately understand the value of purity, and immutable data because they have been burned by the problems that crop up when you try to write threaded programs using shared mutable memory.
On the other hand if you take a 20 year old student still doing their undergraduate degree (like many of the people in the classes I TA), and try to explain the value of immutable data, many of them just don't get it. It has nothing to do with their intelligence or age, but the fact that they haven't written enough code to develop a sense of why such a thing would be useful.
If you want example apps their are plenty littering the internet all covering the various web frameworks, for example here is one covering Happstack: http://happstack.com/docs/crashcourse/index.html
On the other hand if you take a 20 year old student still doing their undergraduate degree (like many of the people in the classes I TA), and try to explain the value of immutable data, many of them just don't get it. It has nothing to do with their intelligence or age, but the fact that they haven't written enough code to develop a sense of why such a thing would be useful.
If you want example apps their are plenty littering the internet all covering the various web frameworks, for example here is one covering Happstack: http://happstack.com/docs/crashcourse/index.html