would be interesting to see the exact lines of code that generated this error, i can't see how to produce it with what you described :P

here's simple example of how to generate it, you should be able to see what's happening:

Code:
//var %x = $!eval(%x,2) | noop $eval(%x,2)

"The only excuse for making a useless script is that one admires it intensely" - Oscar Wilde