In the testing I did, apparently an inline split is faster than using the -F command line arg... here's my results

# File stats ;)
code/monks> wc -l input.list
   5202 input.list

# my way
code/monks> time perl -n -a -e'END { print "$v\t$k\n" while($k,$v)=eac
+h%h} $h{(split(/\|/))[9]}++' input.list
846     10.155.240.2
943     10.155.240.3
3413    10.155.240.1
0.160u 0.000s 0:00.15 106.6%    0+0k 0+0io 339pf+0w

# your way
code/monks> time perl -n -a -F\\\| -e'END { print "$v\t$k\n" while($k,
+$v)=each%h} $h{$F[9]}++' input.list
846     10.155.240.2
943     10.155.240.3
3413    10.155.240.1
0.310u 0.000s 0:00.30 103.3%    0+0k 0+0io 336pf+0w
[download]

As the file got bigger the gap widened.. I started with maybe 100 lines or so, and the difference was non-existant, but once I hit 1000, my way was maybe 25% faster, at 5200 lines my way appears to be 50% faster...

While I was posting I decided to go ahead and create a really big file just for fun.. heres the output

# again stats... 
code/monks> ls -l input.list
-rw-r--r--    1 ericmc   users     2477055 2003-04-09 21:42 input.list
code/monks> wc -l input.list
 100202 input.list

# my way 
code/monks> time perl -n -a -e'END { print "$v\t$k\n" while($k,$v)=eac
+h%h} $h{(split(/\|/))[9]}++' input.list
16046   10.155.240.2
17948   10.155.240.3
66208   10.155.240.1
2.720u 0.020s 0:02.73 100.3%    0+0k 0+0io 339pf+0w

# your way.. 
code/monks> time perl -n -a -F\\\| -e'END { print "$v\t$k\n" while($k,
+$v)=each%h} $h{$F[9]}++' input.list
16046   10.155.240.2
17948   10.155.240.3
66208   10.155.240.1
5.610u 0.010s 0:05.62 100.0%    0+0k 0+0io 336pf+0w
[download]

So it doesnt look like it matters after a certain size, but at least it shaves that little bit extra off.. ;)

Update: Im noticing that you aren't actually sorting anything in perl.. it could be that your time is getting chewed up however you are doing your sorting.. I would move from a one liner to say..

#!/usr/bin/perl
# update2: this is parse.pl 

while (<>) {
   $f = ( split('\|') )[9];

# this needs to get optomized..
   ($data{$f}->[0] = $f) =~ s/\.//g unless( $data{$f} ); 
   $data{$f}->[1]++;
}

for ( sort { $data{$a}->[0] <=> $data{$b}->[0] } keys %data ) {

   print "$data{$_}->[1]\t$_\n";
}

Sample run, Note after each run I go through and change one of the lin
+es so that we arent running into OS caching.

# file statscode/monks> wc -l input.list                              
+                       100202 input.list
code/monks> ls -l input.list
-rw-r--r--    1 ericmc   users     2410847 2003-04-09 22:11 input.list

# and the first way
code/monks> time perl -n -a -F\\\| -e'END { print "$v\t$k\n" while($k,
+$v)=each%h} $h{$F[9]}++' input.list
16046   10.155.240.2
17948   10.155.240.3
66208   39.39.39.39
5.490u 0.000s 0:05.49 100.0%    0+0k 0+0io 336pf+0w

# now for my first iteration without sorting..
code/monks> time perl -n -a -e'END { print "$v\t$k\n" while($k,$v)=eac
+h%h} $h{(split(/\|/))[9]}++' input.list
17948   10.155.240.3
66208   39.39.39.39
16046   40.40.40.40
2.750u 0.000s 0:02.74 100.3%    0+0k 0+0io 339pf+0w

# and now with the code from above...
code/monks> time ./parse.pl input.list
66208   39.39.39.39
16046   40.40.40.40
17948   41.41.41.41
2.190u 0.010s 0:02.26 97.3%     0+0k 0+0io 349pf+0w
[download]

YMMV and you may want to sort on the count of hits as opposed to the IP, but thats a simple replace in the sort..

/* And the Creator, against his better judgement, wrote man.c */