Let's consider I have a list of rules:

{Aa->1/2, Av->2/5, Bx->3/7, Ce->4/9, ...}

I want to find all keys that contain "a" letter and change their values to expressions. This means to have as a result:

***Some code here...***
{Aa->ToExpression[1/2], Av->ToExpression[2/5], Bx->3/7, Ce->4/9, ...}

Thanks for any help!

Let's consider I have a list of rules:

{Aa -> 1/2, Av -> 2/5, Bx -> 3/7, Ce -> 4/9, ...}

I want to find all keys that contain the letter "A" and change their values to expressions. This means to have as a result:

***Some code here...***
{Aa -> ToExpression[1/2], Av -> ToExpression[2/5], Bx->3/7, Ce->4/9, ...}