Using the fubarred xml from your question in the CB:

use warnings;
use strict;

my $string = q {...blah...<file fiop="foo" length="304507"/> SyncBookm
+arkRecordType12345·bjbjUU</file>...blah};

my $foo = qr {<file fiop="([a-z]+)" length="(\d+)"/> (.+)(?=</file>)};
 
if ($string =~ m#$foo#) {
   print "\nMatched \"fiop\" label: |$1|\nMatched Length: |$2|\nMatche
+d data: |$3|\n";
} else {
   print "no match \n";
}

print "\nDone \n\n";
[download]

OUTPUT
Matched "fiop" label: |foo|
Matched Length: |304507|
Matched data: |SyncBookmarkRecordType12345?+bjbjU?U?|

Done