It's telling you that you have to "escape" the @ symbol with \ (backslash).
As you know, the @ symbol in PERL signifies an array identifier. If you use the @ symbol in a string (abc@xyz), perl thinks you're trying to do something with array xyz. Your error message would seem to indicate an improper use of the array in a string - something like "@Lcounter" or '@Lcounter' (note the quotation marks). Maybe you could post your code?
There's always a better way. The fun is trying to find it!