Ten Thousand,10000, 2710 ,,"10,000","It's ""10 Grand"", baby",10K

# Either some non-quote/non-comma text . . . 
[^",]+
#  . . . or . . . 
 |
#  . . . a double-quoted field (inside, paired double quotes are allowed)
" # field's opening quote
 (?: [^"] | "" )*
" # field's closing quote

# Either some non-quote/non-comma text . . . 
( [^",]+ )
#  . . . or . . . 
 |
# . .. a double-quoted field (inside, paired double quotes are allowed)
" # field's opening quote
 (   (?: [^"] | "" )*   )
" # field's closing quote

while ($line =~ m{
           # Either some non-quote/non-comma text . . . 
           ( [^",]+ )
           #  . . . or . . . 
            |
           #  . . . a double-quoted field ("" allowed inside)
           " # field's opening quote
            (   (?: [^"] | "" )*   )
           " # field's closing quote
        }gx)
{
   if (defined $1) {
       $field = $1;
   } else {
       $field = $2;
       $field =~ s/""/"/g;
   }
   print "[$field]"; # print the field, for debugging
   Can work with $field now . . . 
}

[Ten Thousand][10000][ 2710 ][10,000][It's "10 Grand", baby][10K]

(?:^|,)
(?:
    # Either some non-quote/non-comma text....
    ( [^",]* )
  # ... or...
  |
    # ... a double-quoted field (inside, paired double quotes are allowed)
    " # field's opening quote
     (  (?: [^"] | "" )*   )
    " # field's closing quote
)

(?:^|,)
(?: # Now, match either a double-quoted field (inside, paired double quotes are allowed) . . . 
        " # (double-quoted field's opening quote)
         (   (?: [^"] | "" )*   )
        " # (double-quoted field's closing quote)
  | 
    #  . . . or, some non-quote/non-comma text . . . 
        ( [^",]* )
)

import java.util.regex.*;
   
Pattern fieldRegex = Pattern.compile(
   "\\G(?:^|,)                                  \n"+
   "(?:                                         \n"+
   "   # Either a double-quoted field ...       \n"+
   "   \"  # field's opening quote              \n"+
   "    (   (?: [^\"]++ | \"\" )*+   )          \n"+
   "   \"  # field's closing quote              \n"+
   " #  ... or ...                              \n"+
   " |                                          \n"+
   "   # ... some non-quote/non-comma text ...  \n"+
   "   ( [^\",]* )                              \n"+
   " )                       \n", Pattern.COMMENTS);
Pattern quotesRegex = Pattern.compile("\"\"");
   
// Given the string in 'line', find all the fields . . . 


Matcher m = fieldRegex.matcher(line);
while (m.find())
{
    String field;
    if (m.group(1) != null) {
        field = quotesRegex.matcher(m.group(1)).replaceAll("\"");
    } else {
        field = m.group(2);
    }
    // We can now work with the field . . . 
    System.out.println("[" + field + "]");
}

Imports System.Text.RegularExpressions
   
Dim FieldRegex as Regex = New Regex( _
       "(?:^|,)                                        " & _
       "(?:                                            " & _
       "   (?# Either a doublequoted field ...)        " & _
       "   ""  (?# field's opening quote )             " & _
       "    (   (?> [^""]+ | """" )*   )               " & _
       "   ""  (?# field's closing quote )             " & _
       " (?# ... or ...)                               " & _
       " |                                             " & _
       "   (?# ... some non-quote/non-comma text ...)  " & _
       "   ( [^"",]* )                                 " & _
       " )", RegexOptions.IgnorePatternWhitespace)

Dim QuotesRegex as Regex = New Regex("""""") 'A string with two double quotes
    
Dim FieldMatch as Match = FieldRegex.Match(Line)
While FieldMatch.Success
   Dim Field as String
   If FieldMatch.Groups(1).Success
     Field = QuotesRegex.Replace(FieldMatch.Groups(1).Value, """")
   Else
     Field = FieldMatch.Groups(2).Value
   End If

   Console.WriteLine("[" & Field & "]")
   ' Can now work with 'Field'....

   FieldMatch = FieldMatch.NextMatch
End While