Dynamically define a variable in LESS CSS

Question

I am trying to create a mixin that dynamically defines variables in LESS CSS, by actually assigning them a composite name.

The simplified use-case (not the real one)

Answer 1

To follow up on the accepted answer you can also define a value for the variable by extending the .define() mixin as follows. This allows you to use a temporary set of variables within a rule.

.define(@var, @val) {
  .foo() when (@var = temp1) {
    @temp1: @val;
  }
 .foo() when (@var = temp2) {
    @temp2: @val;
  }
 .foo() when (@var = temp3) {
    @temp3: @val;
  }
  .foo();
}

.define(temp2, 2);
.test {
  .define(temp1, 0);
  prop: @temp1;
}
.test2 {
  prop: @temp2;
}

CSS Output

.test {
  prop: 0;
}
.test2 {
  prop: 2;
}

Here is a more complicated gist of how I use this in a mixin for generating responsive background images with background-size: cover; (and an IE8 fallback).