Allowing only specified values of path parameter

[antimatter96]

I want routes like

/savings/all/:userid     

/savings/:service/:userid

The service is limited to say 7. Small enough to do something like /savings/{ec2 || emr || ops}:service but large that we cant write different handlers for all.
Is there any way to limit this type of usage ?

Since service are currently only 3 letter words, can we do something like

/savings/[a-z]{3}:service/:userid     

/savings/summary/:userid

Edit:
Currently I am doing

/savings/aws/all/:userid"
/savings/aws/:service/:userid"

But it gives existing wildcards

[meeDamian]

Quite disappointing it's not available in this otherwise perfect router :/.