if your data file is large, you might see some performance benefit from using a split instead of a more complicated regex:

# skip the header line, assuming it's the first line
# otherwise, you'll have to check in the loop to see
# if you have grabbed a number or a string
my $header = <FILE>;
my $total = 0;
my $count = 0;
while(<FILE>) {
  $total += (split('"', $_))[3];
  $count++;
}
print "Average: ",$total/$count, "\n";
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if you have multiple header lines inside the file, you will need to check in the loop to make sure that you skip the header lines.