Your requirements:

I need to take the first x co-ord in file 1, and substract the x value in file 2 from it - repeat for all x values in file 2.

My code: 

use strict;
use warnings;
$|++;

use constant X => 0;
use constant Y => 1;
use constant Z => 2;

# take the first x co-ord in file 1
my @f1_coords = do {
    my $filename = 'file1';
    open( my $fh, "<$filename" )
        or die "Cannot open '$filename' for reading: $!\n";
    my $line = <$fh>;
    close $fh;
    split( ' ', $line );
};

# substract the x value in file 2 from it - repeat for all x values in
+ file 2
my $filename = 'file2';
open( my $fh, "<$filename" )
    or die "Cannot open '$filename' for reading: $!\n";

my $outname = 'file3';
open( my $out_fh = ">$outname" )
    or die "Cannot open '$outname' for writing: $!\n";

while (my $line = <$fh>)
{
    my @f2_coords = split( ' ', $line );

    print $out_fh $f1_coords[X] - $f2_coords[X], $/;
}

close $out_fh;
close $fh;

[download]

You will want to read through my code a few times. It contains a ton of Perl idioms that may help you learn your way. Enjoy!

------
We are the carpenters and bricklayers of the Information Age.

Then there are Damian modules.... *sigh* ... that's not about being less-lazy -- that's about being on some really good drugs -- you know, there is no spoon. - flyingmoose

I shouldn't have to say this, but any code, unless otherwise stated, is untested

In reply to Re: hash or nest loop by dragonchild
in thread hash or nest loop by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.