As an option to reading line by line from a file handle, the technique in Re: Muy Large File might be adapted.. the sysread, sysseek, syswrite are builtins. IIRC the original goal of that OP was in-place replacement of strings, but you might be able to locate the IPs and then the start and end of lines (packets) by this method... I saved this one because it's so fast for reading and ripping through files off disk.