#Here is  some UNTESTED PSEUDOCODE  to show the idea. There are 2 basic functions. One is send out the form, the second is to receive a response from the form and process it. My cgi is rusty, so anyone who can fix the errors, please do.

#!/usr/bin/perl
use warnings;
use strict;
use CGI;

my( $q ) = new CGI;

print $q->header;
print $q->start_html( -title=>"Test" );
print $q->start_form(-action=>'this_script.cgi);

# Add images
# image_button() produces a clickable image.  When its clicked on the
#  position of the click is returned to your script as "button_name.x" and
# "button_name.y", where "button_name" is the name youve assigned to it.
print $q->image_button(button_name1, /path/source/URL, MIDDLE);
print $q->image_button(button_name2, /path/source/URL, MIDDLE);
print $q->image_button(button_name3, /path/source/URL, MIDDLE);

print $q->submit( -name=>'Choose Action', -label=>'Start Test' );
print $q->br;

print $q->end_form;
print $q->end_html;

# this is where you detect which button is pressed
if ( $q->param() ) {
my $button = $query->param(); 
#probably need better param  checking
#use 
#@params=$query->param; 
#gets a list of all the names of the parameters passed to the script
print "@params\n";

if ($button eq 'button_name1'){'do something'}
if ($button eq 'button_name2'){'do something'}
if ($button eq 'button_name3'){'do something'}

}