If you liked the pack solution, here's a more versatile version (with some additional test data):

#!/usr/bin/env perl

use strict;
use warnings;

my (@data, @max);

while (<DATA>) {
    push @data => [ split /,/ ];

    @max = map { 
        my $len = length $data[$#data][$_];
        ( $max[$_] ||= 0 ) >= $len ? $max[$_] : $len;
    } 0 .. $#{$data[$#data]} - 1;
}

my $template = 'A' . join(A => ( map { $_ + 1 } @max ), '*');
print pack $template => @$_ for @data;

__DATA__
Account,Login Name,Password,Web Site,Comments,Extra
Google Docs,george123,F0oB@r,http://www.google.com/docs,The GoodleDocs
+ site,A
Amazon,george123,fo0bA7,http://www.amazon.com,The Amazone Kindle site,
+B
Apple,george123,mM_B39Aa,https://www. ... shorter,My Apple account,C
Longer Account,Login Name,Password,Web Site,Comments,D
Account,Longer Login Name,Password,Web Site,Comments,E
Account,Login Name,Longer Password,Web Site,Comments,F
Account,Login Name,Password,Longer Web Site,Comments,G
Account,Login Name,Password,Web Site,Longer Comments,H
XAccount,XLogin Name,XPassword,XWeb Site,XComments,I
[download]

Output:

$ pm_pack_fmt_txt.pl
Account        Login Name        Password        Web Site             
+      Comments                Extra
Google Docs    george123         F0oB@r          http://www.google.com
+/docs The GoodleDocs site     A
Amazon         george123         fo0bA7          http://www.amazon.com
+      The Amazone Kindle site B
Apple          george123         mM_B39Aa        https://www. ... shor
+ter   My Apple account        C
Longer Account Login Name        Password        Web Site             
+      Comments                D
Account        Longer Login Name Password        Web Site             
+      Comments                E
Account        Login Name        Longer Password Web Site             
+      Comments                F
Account        Login Name        Password        Longer Web Site      
+      Comments                G
Account        Login Name        Password        Web Site             
+      Longer Comments         H
XAccount       XLogin Name       XPassword       XWeb Site            
+      XComments               I
[download]

You could also use this technique to create a FORMAT for printf (as suggested by toolic++ earlier).

Update: s/@max[0 .. $#max]/@max/