Can someone tell me if these two scripts will produce the EXACT same results?

orig.pl > out1
mod.pl > out2
diff out1 out2
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See also:

• Read Writeup Formatting Tips, then modify your post, using code tags.
• perltidy is a way to automate coed layout (whitespace).

UPDATE: from perlsyn:

Perl is a free-form language: you can format and indent it however you like. Whitespace serves mostly to separate tokens, unlike languages like Python where it is an important part of the syntax, or Fortran where it is immaterial.

Hello, I have just started to learn Perl.

Great. This is a good place to start, and you've picked a fun language to learn with.

Since you're just getting started, go to http://perldoc.perl.org and read perlintro. The question you're asking is addressed in the section titled, "Basic Syntax Overview". There it explains the rules regarding whitespace. But do read through that full document. It will hasten your learning experience, and takes advantage of the fact that many of the questions you're likely to come up with in the first few days have already been answered in one concise document.

Please say you didn't, you know, actually do something foolish like actually trying it yourself? That'd have been sheer madness threatening the very fabric of space/time itself.

(Not that one can see any differences since you neglected to use <code></code> tags around your samples.)

While I cannot see the changes you made in your example (a problem with node formatting), the answer is yes, you can use whitespace. In fact, please add (a reasonable amount of) whitespace. Separate any logical blocks of code you have with an extra linebreak. I generally sprinkle one after (a group of) variable declarations, too. (But I hate "double-spaced" code.)

Also, use tabs to indent your code. Configure your editor to show them as n spaces, where n is a comfortable value (for you). I generally use a value of two spaces, but whenever I'm reading code I'm unfamiliar with, I'll increase it temporarily to four. It helps me understand the flow better.

You might also like the /x modifier if you're working with regular expressions. And if you don't have a syntax-colouring editor yet, get one immediately! It will help tremendously.

Here's what my code looks like, to give you a rough idea on what I consider OK spacing:

sub lint {
    my ($fn) = $_;

    $fn = decode_utf8($fn);

    if ($fn ne (my $new_fn = compose($fn))) {
        print STDERR "Decomposed unicode: $new_fn\n";
        if (!DRY_RUN) {
            die if -e $new_fn;
            rename($fn, $new_fn) or warn "Failed rename for file $fn";
        }
    }

    if (-f $fn) {
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Some editors have “Perl Tidy” tools that will automatically reformat source-code without changing it, in order to improve visual consistency within the code.   Yes, such changes can be a big improvement, because we are extremely visual creatures.

One thing can be a problem, though ... if you reformat an entire module, a source code control system will perceive that the entire module has been changed.   Therefore, what I often prefer to do is to highlight a particular block of code, reformat it automatically, then check-in the file with an appropriate comment.   Then, separately, make the changes that I am contemplating, and check those in again.   This creates a much clearer history of what was changed and why.   Gradually, over the course of time, but only in the areas currently receiving attention for other reasons, the visual quality of the code will improve.

Instead of adding what would generally be considered excess white space, try setting your editor to use a larger font.

Generally more important than white space is that you always use strictures (use strict; use warnings;) to tell you early about silly errors such as typos.

It's much harder to see and understand stuff that isn't there. Avoid using the default variable $_ where you can use a meaningfully named variable instead. Consider:

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

my @lines = `perldoc -u -f atan2;`;

for my $line (@lines) {
    $line =~ s/\w<([^>]+)>/\U$1/g;
    print $line;
}
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