Hallowed monks,

lowly Perl apprentice here with a question regarding list traversal.

I chanced upon this code written in a lesser language:

import sys

f = open(sys.argv[1], "r")
for line in f:
    for n in line.split()[::-2]:
        sys.stdout.write(n + " ")

    print("");

[download]

Being ever curious I wondered how this could be done in Perl.

Trying to wield what little power of Perl I possess, I came up with the following: 

use strict;
use warnings "all";

open(my $fh, "<", "$ARGV[0]") or die;
while (<$fh>)
{
    chomp;
    my $i = 0;
    map {print $i++ & 1 ? "" : "$_ "} reverse split(/ /);
    print "\n";
}
close $fh;

[download]

The task seems simple at a glance:

Given a line of numbers from a file, print every 2nd number starting from the back.

Example:

1 22 3 -4 ==> -4 22

Are the esteemed monks able to enlighten me with a solution that is better and more performant?

Faithfully yours,

Perl apprentice

In reply to printing every 2nd entry in a list backwards 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.