Try this:

#! /usr/bin/perl

my $string = q/allow:test1,"@test, 2 " deny:test3,test4 password:"123 
+  456doh:"/;

while ($string =~ s/(\w+):((\w+|"[\w ,:@]+")(,\s*(\w+|"[\w ,:@]+"))*)\
+s*($|(?=\w+:))//) {
  print "Argument: $1\n";
  my $paramlist = $2;
  while ($paramlist =~ s/(\w+|"[\w ,:@]+")\s*,*\s*//) {
    print "  Param: $1\n";
  }
}
[download]

However the regexp is starting to get a bit complicated - Text::ParseWords looks like a neater solution.

JJ