ruby on rails - How can I change this from a local to instance variable? -

i have block of code:

if %w[ups fedex usps].include?(carrier.slug)   send(carrier.slug).track(number) end 

which replicates:

ups.track(number) fedex.track(number) usps.track(number) 

but need that, instance variables:

@ups.track(number) @fedex.track(number) @usps.track(number) 

what's equivalent?

if %w[ups fedex usps].include?(carrier.slug)   var_name = "@#{carrier.slug}"   instance_variable_get(var_name).track(number) end 

by way, interpretation incorrect.

ups.track(number) fedex.track(number) usps.track(number) 

these treated methods, not local variables. if there's no method ups, code fail (even if there local var same name).