One expression to get the first letter of a string and capitalize it

[Peng Yu]

x=abc
y=${x:0:1}
echo "${y^^}"

I want to get the first letter of a string and capitalize it. Ideally,
I want it to be done in one expression. But I only know how to do it
with two expressions.

Is there a way to do it in a more concise manner (without using an
extra variable, or definition of a new function, etc)?

-- 
Regards,
Peng