#!/usr/bin/perl
use strict;
use warnings;

open my $file, '<', "file.txt" or die $!;
open my $out, '>', "newfile.txt" or die $!;
for (1..2) {
    my $constant = <$file>;
    print $out $constant;
}
while (<$file>) {
    my ($name, $time) = (split /\s+/, $file)[1,9];
    my ($net, $sta) = (split /\s+/, $name)[0,1];
    if ($net eq "ZJ") {
        
    }
    # Calculate the mean of the 9th column for every first column that begins with ZJ,
    # and subtract the mean from each value (time) in the 9th column.
}


# Output the new file with the mean removed from each "time" in the 9th column