Your syntax is wrong is all.
[cubescript]loop i 10 [echo hello world][/cubescript]
or
[cubescript]loop i 10 [echo "hello world"][/cubescript]
or
[cubescript]loop i 10 [echo [hello world]][/cubescript]
All do the same thing. By putting parenthesis around the string cubescript was trying to execute alias "hello world" which doesn't exist, and because it has whitespace prolly made the parser very angry. :P
[cubescript]loop i 10 [echo hello world][/cubescript]
or
[cubescript]loop i 10 [echo "hello world"][/cubescript]
or
[cubescript]loop i 10 [echo [hello world]][/cubescript]
All do the same thing. By putting parenthesis around the string cubescript was trying to execute alias "hello world" which doesn't exist, and because it has whitespace prolly made the parser very angry. :P