Set a default variable in nginx with set

Question

In nginx I can use set to define a variable, but is it possible to define a default?

e.g.

set $foo bar if $foo is not defined

Answer 1

map $foo $new_foo {
    default  $foo;
    ''       bar;
}

or

if ($foo = '') {
    set $foo bar;
}

• http://nginx.org/r/map
• http://nginx.org/r/if