I routinely use this little script to emulate webapps running under Apache::Registry. It evals another perl source file as a subroutine and then calls it many times. This is exactly what Apache::Registry does to all scripts for which it is configured to be a PerlHandler.

#! /usr/bin/perl -w
use strict;

use File::Slurp;

use lib '/site/perl';

@ARGV >= 2 or die "Args: <perl program> <rep count> ...\n";

my $victim = read_file(shift @ARGV);

eval "
sub victim { "
. $victim .
" } ";

open STDOUT, ">", "/dev/null";
open STDERR, ">", "/dev/null";

victim() for 1 .. shift @ARGV;
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This approach works best with CGI.pm enabled scripts so I can pass query-params on the command line. I use the above script (called profile.pl) this way:

perl -d:Profile tools/profile.pl mail.cgi 500 mode=mailbox mbox=INBOX 
+page=4 sort=vSUBJ
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So I run 500 iterations of one of my most intensive code paths under Devel::Profile (alas, Devel::DProf breaks Unicode::String in a very weird way). Try it.

Btw, I use HTML::Template and it needs lots of CPU time. I was very surprised to find my most annoying bottleneck in output page generation.