Just a comment on your code, not exactly related to what you've asked, but here goes anyway, as I was just reading about this last night. You have these two lines.

($JUNK, $user, $JUNK) = split (/\s+/, $data_line);
...
($user, $IP, $machine, $VER, $JUNK, $PID, $JUNK, $SDAY, $SDATE, $start
+_time) = split (/\ /, $data_line);
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When assigning to a list, you can assign to undef to throw away a value, thereby not creating a useless variable.

(undef, $user, undef) = split (/\s+/, $data_line);
...
($user, $IP, $machine, $VER, undef, $PID, undef, $SDAY, $SDATE, $start
+_time) = split (/\ /, $data_line);
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This is explained in perldata, under 'List value constructors'. It also gets rid of the need to declare $JUNK if you enable strict 'vars', which you probably should consider if you haven't already done so.