Q:

Twig: Print the value of a variable where the variable name is String

I have a variable named e.g. var1 which has value value1 as string.
How can I print the value of variable var1 where var1 is obtained as string?
Let 
{{ set container = 'var1' }}

The value of the variable container is dynamic. Depending on the value of container, I need to print its value; in this case, I need to print the 'value1'.
I am looking for something like this 
{{ attribute(this, container) }} /* <= This will not since this is not defined in Twig */

A:

Turns out I was wrong.
You can use the _context variable which contains all variables passed to the template. 
Try {{ dump(_context) }}
Relevant Documentation
You can create a function that gets passed this context and the array key to access that value.
This twig function should work fine:
public function getAttribute($context, $key)
{
    if (!array_key_exists($key, $context)) {
        return '';
    }

    return $context[$key];
}

With the variables being passed title=foo and another variable being passed refTitle=title, this should output "foo".
{{ attribute(_context, refTitle) }}

