Simple PERL script to loop very quickly - perl

Question

I'm trying to get a perl script to loop very quickly (in Solaris).
I have something like this:
#! /bin/perl
while ('true')
{
use strict;
use warnings;
use Time::HiRes;
system("sh", "shell script.sh");
Time::HiRes::usleep(10);
}
I want the perl script to execute a shell script every 10 microseconds. The script doesn't fail but no matter how much I change the precision of usleep within the script, the script is still only being executed approx 10 times per second. I need it to loop much faster than that.
Am I missing something fundamental here? I've never used perl before but I can't get the sleep speed I want in Solaris so I've opted for perl.
TIA
Huskie.
EDIT:
Revised script idea thanks to user comments - I'm now trying to do it all within perl and failing miserably!
Basically I'm trying to run the PS command to capture processes - if the process exists I want to capture the line and output to a text file.
#! /bin/perl
while ('true')
{
use strict;
use warnings;
use Time::HiRes;
open(PS,"ps -ef | grep <program> |egrep -v 'shl|grep' >> grep_out.txt");
Time::HiRes::usleep(10);
}
This returns the following error:
Name "main::PS" used only once: possible typo at ./ps_test_loop.pl line 9.

Answer 1

This is a pure perl program (not launching any external process) that looks for processes running some particular executable:
#!/usr/bin/perl
use strict;
use warnings;
my $cmd = 'lxc-start';
my $cmd_re = qr|/\Q$cmd\E$|;
$| = 1;
while (1) {
opendir PROC, "/proc" or die $!;
while (defined(my $pid = readdir PROC)) {
next unless $pid =~ /^\d+$/;
if (defined(my $exe = readlink "/proc/$pid/exe")) {
if ($exe =~ $cmd_re) {
print "pid: $pid\n";
}
}
}
closedir PROC;
# sleep 1;
}
On my computer this runs at 250 times/second.

Answer 2

The bottleneck is the creation of processes, pipes, and opening the output file. You should be doing that at most once, instead of doing it in each iteration. That's why you need to do everything in Perl if you want to make this faster. Which means: don't call the ps command, or any other command. Instead, read from /proc or use Proc::ProcessTable, as the comments suggest.
Incidentally: the use statement is executed only once (it is essentially a shorthand for a require statement wrapped in a BEGIN { } clause), so you might as well put that at the top of the file for clarity.