It is possible to program Linino to send HTTP requests and then use the returned values in sketch?
Take a look at Bridge example or TemperatureWebPanel example: you see you can receive kind of "commands" and react "doing things".

Then take a look at HTTP Client example, where you delegate an HTTP call to the linux side.

Now mix the two: you can make HTTP calls after receiving a command from outside your Yun.

A short test can be done by cutting and pasting the examples above.