Try this, it'll take around 10 seconds:

perl -ple"BEGIN{ $/ = \80 }" theBigFile > theNewFile
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If you only want to break lines after a comma, then it's a tad more complicated:

(Note:one-liner wrapped for posting!)

perl -e"BEGIN{$/=\80}" 
-nle"$x.=$_; print $1 while length($x)>80 and $x=~s[(.{1,80},)(?!,)][]
+"
 theBigFile > theNewFile
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use Text::Wrap qw( wrap );

local $Text::Wrap::columns = 80;
print wrap('', '', <IN>);
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Text::Wrap

Update: I misunderstood the question and missed the magnitude of the file!

use Text::Wrap qw( wrap );

local $Text::Wrap::columns = 80;
local $Text::Wrap::break   = qr/(?<=,)/;
local $/ = ',';
print wrap('', '', $_) while <IN>;
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Downside: Will break on every comma, even those in the middle of a field.

You can get rid of the Text::Wrap entirely if none of the fields are overly large.

I hope that file contains some whitespace, otherwise it'll chew a heap of cpu and gobs of memory and take a very long time.

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

I noticed and updated the node while you were replying.

You can read fixed-size chunks from your file handle. Then do your splitting similar to what you're doing now. Just set your input record size like so:

local $/ = \500;
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Then you can chop it up into approximately 80 character lines breaking on the commas like you're doing now, and when you need more text (say, when you have less than 100 characters left, read another chunk and append it to your text buffer). Here's an example of how you might approach it. (Note: rather than worry about 80 character lines, I'm just writing 10 values on each line.)

#!/usr/bin/perl -w
use strict;
use warnings;
local $/ = \500;
open IN, '<', 'bigfile.csv' or die $!;

my @values;
while (my $line = <IN>) {
    push @values, split /,/, $line;
    while (@values > 10) {
        print join(',',@values[0..9]), "\n";
        @values = @values[10..@values-10];
    }
}
close IN or die $!;
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...roboticus

UPDATE: D'oh! ikegami's solution looks much better... Ah, well. I guess I need to read Text::Wrap now...

perl -ne 'BEGIN{$/=","} $o.=$_; if(length($o)>=80){ print "$o\n";$o=""
+ }
  END{print "$o\n"}' < file.no-breaks > file.with-breaks
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Then again, when the purpose of a data file is simply to store list, I personally don't see the point of using commas at all. It's much better to use line-breaks as delimiters between list elements, because then you can use lots of handy unix tools to good effect in order to do things like (de)select, count, sort or otherwise process the elements. And going from comma-delimited (with no line-breaks) to line-break delimited is really simple:

perl -pe 'tr/,/\n/' < comma.delimited > newline.delimited
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