That's what map is for:

my @result = map { [split /\s+/] } split /\n/, $cmd_output
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That leaves you with an array of arrays like [ ['2009-11-05 17:59:52', '1.501'], ...]. If you prefer a hash, simply make it

my %result = map { (split /\s+/) } split /\n/, $cmd_output
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You probably have to ensure you exclude the header lines in your input file, like so:

my @result = map { [split /\s+/] } grep { /^\d+/ } split /\n/, $cmd_ou
+tput
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This only processes lines that start with a couple of numbers. It should be sufficient in this case. Read up about grep, map and sort. They're powerful tools.