I don't think that you want to print this out after every loop. I think you want to print out after every day. Maybe try this. Also I think the way you are looping through the lines is a little messed up. The while is looping through the lines, and the until really isn't doing anything.

Try something like this(untested):

#!/usr/bin/perl -w -d
use strict;
my $date;
my $line;
my ($tot_ip_cnt,$tot_icmp_cnt,$tot_tcp_cnt,$tot_udp_cnt,$tot_events,$t
+ot_drops) = (0,0,0,0,0,0);

open (INFILE, "< hbeat-app.log.samp") or die ("Error Opening File $!\n
+");   
open (OUTFILE, ">> HB_APP_totals.log.CSV") or die ("Error Opening File
+ $!\n");
print OUTFILE "date,ip_cnt,icmp_cnt,tcp_cnt,udp_cnt,events,drops \n";

while ( my $line = <INFILE>) {
   if ($line =~ m/^(\d{4})(\w{3})(\d+).+/) {
        print OUTFILE "$date,$tot_ip_cnt,$tot_icmp_cnt,$tot_tcp_cnt,$t
+ot_udp_cnt,$tot_events,$tot_drops\n" if(length($date) > 0);
     $date = join ' ',($2,$3,$1);
   } else {
     $line =~ m/^EVENT1\:\s+\[\w+\]\s+\(IP\=(\d+)\,ICMP\=(\d+)\,TCP\=(
+\d+)\,UDP\=(\d+)\,EVENTS\=(\d+)\,DROP\=(\d+)\,.+/;
     $tot_ip_cnt += $1;
     $tot_icmp_cnt += $2;
     $tot_tcp_cnt += $3;
     $tot_udp_cnt += $4;
     $tot_events += $5;
     $tot_drops += $6;
   }
}

print OUTFILE "$date,$tot_ip_cnt,$tot_icmp_cnt,$tot_tcp_cnt,$tot_udp_c
+nt,$tot_events,$tot_drops\n";

close OUTFILE;
close INFILE;
[download]

Update: Added print after loop to print out last day.