I would really recommend a module for this sort of thing. For example using XML::Simple:

use strict;
use warnings;
use XML::Simple;
use Data::Dumper;

my $string = do { local $/; <DATA>};
my $ref = XMLin($string);
print Dumper $ref;

my $num_events = @{$ref->{EVENT}};
print "There are $num_events events listed\n";
__DATA__
<ROOT>
<EVENT>
 <NAME>test2</NAME>
 <LOCATION>iwu</LOCATION>
 <TIME>now</TIME>
 <DATE>today</DATE>
 <PRIORITY>interest</PRIORITY>
 <ATTENDEES>a lot</ATTENDEES>
 <DESCRIPTION> descrip</DESCRIPTION>
</EVENT>
<EVENT>
 <NAME>test3</NAME>
 <LOCATION>hi</LOCATION>
 <TIME>joe</TIME>
 <DATE>how</DATE>
 <PRIORITY>interest</PRIORITY>
 <ATTENDEES>are</ATTENDEES>
 <DESCRIPTION> </DESCRIPTION>
</EVENT>
</ROOT>
[download]

As for the code you posted you need to add the /s modifier or the .'s will not match the newline characters (will not cross over lines). If it were me and was doing a quick hack I would probably still use XML::Simple, but as for changing your regex to capture multiple matches you might try something like the following:

my @events;
while ($page_body =~ /<EVENT>(.*?)<\/EVENT>/sg){
 push @events, $1 #note $1 might have zero length.  
}
[download]

Also note that it is pointless to have .*? at the very start of a regular expression as it will cause a lot of of needless backtracking, and never really match anything, as a regex looks for a pattern anywhere in the string (lest it be anchored)

-enlil