Thats great and thank you very much for your help. I have one further issue though. My existing code now looks like this

#!/usr/bin/perl

use 5.010;
use strict;
use warnings;

while (my $line = <STDIN>) {
chomp($line);
my ( $mon, $day, $time, $dom, $login, $remainder ) =
   split m{:?\s+}, $line, 6;
my %monthNos = do {
   my $no = 0;
   map { $_ => ++ $no }
   qw{ Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec };
   };

my $yr = q{2012};
my $csv = sprintf q{%02d/%02d/%s %s,%s,%s,"%s"},
   $day, $monthNos{ $mon }, $yr, $time, $dom, $login, $remainder;

say $csv;
}
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As I wanted the remainder to be in double quotes so it would read in as one field. The problem is that remainder sometimes already contains double quotes which I would like to remove or replace with single quotes

I tried the following but it leaves be with an empty set of double quotes