Here's some very simple regular expressions to get you started.

#!/usr/bin/perl

use strict;
use warnings;
use diagnostics;

my $msg = <<'MSGEND';
<msg time='2009-10-14T05:46:42.580+00:00' org_id='oracle' comp_id='tns
+lsnr' type='UNKNOWN' level='16' host_id='mtdb_a' host_addr='UNKNOWN' 
+version='1'> <txt>14-OCT-2009 05:46:42 * (CONNECT_DATA=(SID=fgs)(CID=
+(PROGRAM=sqlplus@mtdb)(HOST=mtdb_a)(USER=root))) * (ADDRESS=(PROTOCOL
+=tcp)(HOST=10.60.4.2)(PORT=34898)) * establish * fgs * 0 </txt> </msg
+>
MSGEND

print "msg: $msg\n";

# Isolate content of <txt> tags
if ($msg =~ m{<txt>(.*)</txt>})
{
    my $txt = $1;
    print "txt: $txt\n";

    # Find the date
    if ($txt =~ /(\d{2}-\w+-\d{4})\s+(\d{2}:\d{2}:\d{2})/)
    {
        my ($date, $time) = ($1, $2);
        print "date: $date\n";
        print "time: $time\n";
    }

    # Find the host (IP address, not name)
    if ($txt =~ /HOST=([\d\.]+)/)
    {
        my $host = $1;
        print "host: $host\n";
    }
}
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