How to sort csv file with perl

[Trevor W]

I haven't touched Perl in a while but I ran into a relatively simple parsing problem at work that it would be perfect for. I threw together a program using what I remembered--just want to get comments and see if I'm on the right track:

Data looks like this:

2010-10-05 09:00:00-1000,1,1012,,
2010-10-05 09:00:00-1000,2,397,,
2010-10-05 09:00:00-1000,3,0,,
2010-10-05 09:00:00-1000,4,165,,
 

But what I want is <DT>,1012,397,0,165,,

Pseudocode:

Open the dang file
Remove trailing comma from each line
Remove date from every n+1,n+2,n+3 lines
Remove (1,2,3,4) from every n+1,n+2,n+3 lines
Take final values from every n+1,n+2,n+3 lines and push it onto the end of every n line
Replace trailing comma
Close the dang file
 

So what I want to do is open the file, put it into an array, chomp and chop it, split that array into other arrays, loop through and rewrite each array line with the right subcomponents of each array, offset?

Trial code:

open (DATA,$ARGV[0]); or
    die("File '$ARGV[0]' does not exist?\n");
my @lines = <DATA>;
close DATA or 
    warn $! ? "Error closing pipe: $!"
         "Exit status $? from sort";
 
    chomp @lines;
    / get rid of the second comma after each line /
    chop @lines;
 
    / break up fields into categories by comma /
    (@time,@mtu,@watth) = split "," , @lines;
 
    / move every n+2nd, n+3rd, and n+4th power value up to the nth line /
    $hop = 0;
    while(@lines) {
    @lines[$hop] = @time[$hop],@watth[$hop],@watth[$hop+1],@watth[$hop+2],@watth[$hop+3]",,";
 
    / hop 4 at a time /
    $i+=4;
    }
open (OUT,$ARGV[0]);
 
print OUT @lines;
 

Thanks for your help. I would love to get competent with Perl.