Here's something to illustrate perhaps a little better what I had in mind:

c:\@Work\Perl\monks>perl -wMstrict -le
"use constant MAX => 32_760;
 ;;
 my $s = 'FLAGS xyzzy UID 42 RFC {234565} ' . 'a' x 234565 . 'Y yyyy';
 print substr $s, 0, 50;
 print substr $s, -50;
 print length $s;
 ;;
 my %piece;
 ;;
 PARSE: {
   if ($s =~ m{ \G RFC \s* \{ (\d+) \} \s* }xmsgc) {
     my $total = $1;
     use integer;
     my $n = $total / MAX;
     my $m = $total % MAX;
     $s =~ m{ \G ((?: .{${ \MAX }}){$n} .{$m}) \s* }xmsg or die 'no co
+unt';
     $piece{rfc} = $1;
     redo PARSE;
     }
   elsif ($s =~ m{ \G \s* Y \s* (\w+) \s* }xmsgc) {
     $piece{y} = $1;
     redo PARSE;
     }
   elsif ($s =~ m{ \G UID \s* (\d+) \s* }xmsgc) {
     $piece{uid} = $1;
     redo PARSE;
     }
   elsif ($s =~ m{ \G \s* FLAGS \s* (\w+) \s* }xmsgc) {
     $piece{flags} = $1;
     redo PARSE;
     }
   else {
     last PARSE;
     }
   }
 ;;
 print qq{flags '$piece{flags}'  uid '$piece{uid}'  y '$piece{y}'};
 printf qq{start rfc: '%s' \n}, substr $piece{rfc}, 0, 30;
 printf qq{  end rfc: '%s' \n}, substr $piece{rfc}, -30;
 print 'length rfc: ', length $piece{rfc};
"
FLAGS xyzzy UID 42 RFC {234565} aaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaY yyyy
234603
flags 'xyzzy'  uid '42'  y 'yyyy'
start rfc: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
  end rfc: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
length rfc: 234565
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