Hi,
It doesn't look like fuel line to me, looks more like silcone hose ? & definately not brake pipes ( if it was I would say you would certainly have something to worry about )
It's looks like a breather pipe from the battery or gearbox
I presume the car isn't running at the moment ?
As suggested above the best thing would be follow the pipe to see where it goes.
Don't worry about your good jeans, I used to have some of those but since I bought my Cobra mine are now all ''working trousers'' !!!
Regards Phil.