So, I imagine the headers will never have a time in them? Time has a a ":" in it that should be unique to them. So maybe instead of :

if ($line =~ /^\b\d/)
[download]

You could use

if ($line =~ m/:/)
[download]

I didn't test it since I don't have a sample of your input, but something along those lines should process your steps only if the lines have a colon in them. Alternatively, if the headers and only the headers contain "perf" in them, you could do

if ($line !~ m/perf/)
[download]