Workout of Old Gray Bear's idea: 
my %data;
my $header = <>;  # first line
while(<>) {
    my($key) = split /\t/;
    $data{$key} = $_;
}

# output:
print $header;
foreach my $key (sort keys %data) {
    print $data{$key};
}

[download]
To use it as is, call the script with "file2.txt" as parameter on the command line, and redirect the script's STDOUT to "file1.txt". 
perl thescript.pl file2.txt >file1.txt

[download]

In reply to Re^2: File Manipulation - Need Advise! by bart
in thread File Manipulation - Need Advise! by nashkab

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