LESS Compiler
This free online LESS compiler will generate the final CSS code using your provided LESS source. This tool is best suited for quick tests and for learning LESS. LESS command-line & GUI compilers are available and will probably be better suited for your needs in the long run.
The LESS compiler does NOT support @import instructions, since it introduces external dependencies that are hard to implement for a web-base application. As a workaround, I suggest you provide the compiler with a single LESS file and that you split it after you're done testing.