According to the source code (https://github.com/gleitz/howdoi/blob/master/howdoi/howdoi.p...), the answers come from Stack Overflow, searched using Google site search. Howdoi scrapes and prints the first code block in the top answer, or the full text of the top answer if it contains no code block.
It should probably use symbolhound.com instead, which does exact symbol queries on stackoverflow content. Google, alas, thinks we are all terrible people for wanting our precious bytes.
That's a nice search tool. I found that the relevance is not quite as good as Google (for example "howdoi get referrer url php") but this could be used when you enter a query that contains symbols.
