#!/usr/bin/perl -Tw

# heavily commented for the sake of this post

# presents time in my chosen format
use POSIX qw/strftime/;

# used for the Perl page rendered time I'm trying to produce
use Time::HiRes qw/gettimeofday tv_interval/;

# trickery to send the page as application/xhtml+xml,
# if the client supports it
if ($ENV{'HTTP_ACCEPT'} =~ /application\/xhtml\+xml/)
{
    print "content-type:application/xhtml+xml; charset=utf-8\n\n";
} else {
    print "content-type:text/html; charset=utf-8\n\n";
}
# here's where I start my timer
my $start_time = [gettimeofday];

# just to add some of my local routines to my @INC
use lib './localincs/';

# again, my preferred time format (has nothing to do with my timer)
my $utc_time = strftime('%F %T %z',localtime);

...yadda,yadda,yadda...

# bottom of web page, just before </body></html>
my $total_time = tv_interval($start_time);

# the following line should present something like this:
# Page processed by Perl <my Perl version number> in 0.00001 seconds
# But only produces the Perl version number
printf('Page processed by Perl %s in %.02f seconds',$],$total_time);