$input = '7374,726327,"76,237",32324,"21,342,857",23';
print("input:  $input\n");


$output = '';

foreach ($input) {
   if (/\G("[^"]+")/gc) {
      my $quoted = $1;
      $quoted =~ s/,//g;
      $output .= $quoted;
      redo;
   }

   # Unmatched quote.
   if (/\G"/gc) {
      $output .= '"';
      redo;
   }

   if (/\G([^"]+)/gc) {
      $output .= $1;
      redo;
   }
}

print("output: $output\n");