Site lesscss.org docs error

[tacid]

In docs page http://lesscss.org/docs in the section Operations there is a code listing:

@base: 5%; 
@filler: @base * 2; 
@other: @base + @filler; 

color: #888 / 4;
background-color: @base-color + #111;
height: 100% / 2 + @filler;

But when I was trying to compile it error occurs:

! Variable Name Error: @base-color in * is undefined.

Maybe line color: #888 / 4; must be changed to @base-color: #888 / 4; ?

Thank you