#!usr/bin/perl
use warnings;
use strict;
use Data::Dumper;

my @lines = ('Nov 19 06:31:17 proxy postgrey[2439]: action=pass, reason=triplet found, client_name=r41.newsletter.otto.de, client_address=185.15.51.41, sender=otto@newsletter.otto.de, recipient=some.one@some.domain'
,'Nov 19 06:37:45 proxy postgrey[2439]: action=pass, reason=triplet found, client_name=uspmta194080.emarsys.net, client_address=217.175.194.80, sender=suite17@xpressus.emarsys.net, recipient=other.one@some.domain');

foreach my $line (@lines)
{
   my $hash_ref = parseline ($line);
   my %tokens = %$hash_ref;
   
   print "line=$line\n";
   
   foreach my $key (keys %tokens)
   {
       print "key=$key \t value=$tokens{$key}\n";
   }
   print "\n"; #blank line spacer
}

# parse line creates a hash of keys and values representing
# the contents of the line

sub parseline
{
   my $line = shift;
   
   my %tokens;
   
   my ($beginning_tag, $rest) = split (': ', $line,2);  #space after the : required

   %tokens = ($rest =~ /(\S+)=(.+?)(?:,|$)/g);
   $tokens{tag} = $beginning_tag;
   
   return \%tokens;
}

__END__
Prints:
line=Nov 19 06:31:17 proxy postgrey[2439]: action=pass, reason=triplet found, client_name=r41.newsletter.otto.de, client_address=185.15.51.41, sender=otto@newsletter.otto.de, recipient=some.one@some.domain
key=client_address 	 value=185.15.51.41
key=action 	 value=pass
key=reason 	 value=triplet found
key=recipient 	 value=some.one@some.domain
key=tag 	 value=Nov 19 06:31:17 proxy postgrey[2439]
key=client_name 	 value=r41.newsletter.otto.de
key=sender 	 value=otto@newsletter.otto.de

line=Nov 19 06:37:45 proxy postgrey[2439]: action=pass, reason=triplet found, client_name=uspmta194080.emarsys.net, client_address=217.175.194.80, sender=suite17@xpressus.emarsys.net, recipient=other.one@some.domain
key=reason 	 value=triplet found
key=recipient 	 value=other.one@some.domain
key=action 	 value=pass
key=client_address 	 value=217.175.194.80
key=client_name 	 value=uspmta194080.emarsys.net
key=tag 	 value=Nov 19 06:37:45 proxy postgrey[2439]
key=sender 	 value=suite17@xpressus.emarsys.net