Accessing configuration values by variable ?

[NuggyBuggy]

For some reason I am having trouble wording this.

If you have a configuration
Configuration.for('app') {
key 'value'
foo 'bar'
}

and then
c = Configuration.for 'app'

I know we can access c.key, c.foo.

But is there a way to access a configuration key/value pair when the key is not known explicitly, but by variable ?

e.g. if foo=bar, is there a way to get the key/value pair corresponding to the value of foo ?

thanks !
terry