Yes, clearly I must be, if you get output from that line, because I do not.

I do get output if I enter...

varnishlog -o -i Backend,RxURL,ReqEnd,RxHeader

...and when I enter...

ls | perl -ne 'BEGIN { $/= "";} print'

...but not when I enter...

 varnishlog -o -i Backend,RxURL,ReqEnd,RxHeader | perl -ne 'BEGIN { $/= "";} print'

So both parts of the command work individually, but not together!

Any suggestions as to what I'm missing would be most welcome.

EDIT: Solved it by redirecting the output to a textfile, then grepping the textfile. Still interested in finding out why the Perl command didn't work.