Here is a step-by-step series of code blocks that should equip you with enough knowledge to block any/all necessary entities. Read through the set of code blocks, observe the patterns, and then copy, combine and customize to suit your specific scum-blocking needs:
# set variables for user agents and referers and ip addresses
SetEnvIfNoCase User-Agent ".*(user-agent-you-want-to-block|php/perl).*" BlockedAgent
SetEnvIfNoCase Referer ".*(block-this-referrer|and-this-referrer|and-this-referrer).*" BlockedReferer
SetEnvIfNoCase REMOTE_ADDR ".*(666.666.66.0|22.22.22.222|999.999.99.999).*" BlockedAddress
# set variable for any class B network coming from a given netblock
SetEnvIfNoCase REMOTE_ADDR "66.154.*" BlockedAddress
# set variable for two class B networks 198.25.0.0 and 198.26.0.0
SetEnvIfNoCase REMOTE_ADDR "198.2(5|6)..*" BlockedAddress
# deny any matches from above and send a 403 denied
<Limit GET POST PUT>
order deny,allow
deny from env=BlockedAgent
deny from env=BlockedReferer
deny from env=BlockedAddress
allow from all
</Limit>
