If you are reading data in line by line, you can add elements to arrays using push, eg push @y, $data;. This way, you can read in a line, determine if the data needs to be stored, and push or let it drop.

If you are reading the data in en masse as an array to start, you can use the grep function to detemine which elements stay or go, eg @y = grep { $_ =~ /command/ } @data;

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Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important