I'd just do it with an ordinary split... e.g.

my %emails = ();
foreach ( split(/\%/, $emailcolumn) ) {
  if ( my ($key, $value) = split(/\s*\:\s*/, $_, 2) ) {
    push ( @{ $emails{$key} }, $value);
  }
} # foreach
# do something with %emails
[download]

Then you've got a data structure as the following (Hash of Arrays):

%emails = ( 
  SMTP => [ 'makeusbetter@domain.com', ...],
  X400 => [ 'c=US;a= ;p=domain ;o=domain;s=makeusbetter', ... ],
  smtp => [ ..., ...],
  CCMAIL => [..., ...]
          );
[download]

Beware that exchange sometime delivers SMTP and smtp adresses. I think that the SMTP: is the main address, whereas the smtp: are additional addresses, but am not absolutely sure.

Best regards,
perl -le "s==*F=e=>y~\*martinF~stronat~=>s~[^\w]~~g=>chop,print"