require 'net/pop'
conn = Net::POP3.new('mail.myhost.com')
conn.start('username', 'password')
require 'net/pop'
conn = Net::POP3.new('mail.myhost.com')
conn.start('username', 'password')
conn.mails.each do |msg|
   File.open(msg.uidl, 'w') { |f| f.write msg.pop }
   # msg.delete
end
conn.finish
conn = Net::POP3.new('mail.myhost.com')
conn.start('username', 'password')
ids = conn.mails.collect {|msg| msg.uidl if msg.pop.match('jabba')}
conn.finish

["UID2-1141260595", "UID3-1141260595"]

Error! (Exception?) Here's stdout:
Net::POPAuthenticationError: -ERR incorrect password or account name
	from /usr/lib/ruby/1.8/net/pop.rb:862:in `check_response_auth'
	from /usr/lib/ruby/1.8/net/pop.rb:764:in `auth'
	from /usr/lib/ruby/1.8/net/pop.rb:445:in `do_start'
	from /usr/lib/ruby/1.8/net/pop.rb:432:in `start'
	from (irb):3
Net::POPAuthenticationError: -ERR incorrect password or account name
	from /usr/lib/ruby/1.8/net/pop.rb:862:in `check_response_auth'
	from /usr/lib/ruby/1.8/net/pop.rb:764:in `auth'
	from /usr/lib/ruby/1.8/net/pop.rb:445:in `do_start'
	from /usr/lib/ruby/1.8/net/pop.rb:432:in `start'
	from (irb):6
IOError: POP session not opened yet
	from /usr/lib/ruby/1.8/net/pop.rb:475:in `command'
	from /usr/lib/ruby/1.8/net/pop.rb:488:in `n_mails'
	from /usr/lib/ruby/1.8/net/pop.rb:507:in `mails'
	from (irb):7
IOError: POP session not yet started
	from /usr/lib/ruby/1.8/net/pop.rb:459:in `finish'
	from (irb):11
Net::POPAuthenticationError: -ERR incorrect password or account name
	from /usr/lib/ruby/1.8/net/pop.rb:862:in `check_response_auth'
	from /usr/lib/ruby/1.8/net/pop.rb:764:in `auth'
	from /usr/lib/ruby/1.8/net/pop.rb:445:in `do_start'
	from /usr/lib/ruby/1.8/net/pop.rb:432:in `start'
	from (irb):13
IOError: POP session not opened yet
	from /usr/lib/ruby/1.8/net/pop.rb:475:in `command'
	from /usr/lib/ruby/1.8/net/pop.rb:488:in `n_mails'
	from /usr/lib/ruby/1.8/net/pop.rb:507:in `mails'
	from (irb):14
IOError: POP session not yet started
	from /usr/lib/ruby/1.8/net/pop.rb:459:in `finish'
	from (irb):15

conn2 = Net::POP3.new('mail.myhost.com')
conn.start('username', 'password')
conn.each_mail {|msg| puts msg.pop if msg.uidl=='UID3-1141260595'}
conn.finish

Return-Path: <jabba@huttfoundation.org>
X-Original-To: username@my.mailhost.com
Delivered-To: username@localhost
...

Error! (Exception?) Here's stdout:
Net::POPAuthenticationError: -ERR incorrect password or account name
	from /usr/lib/ruby/1.8/net/pop.rb:862:in `check_response_auth'
	from /usr/lib/ruby/1.8/net/pop.rb:764:in `auth'
	from /usr/lib/ruby/1.8/net/pop.rb:445:in `do_start'
	from /usr/lib/ruby/1.8/net/pop.rb:432:in `start'
	from (irb):17
IOError: POP session not opened yet
	from /usr/lib/ruby/1.8/net/pop.rb:475:in `command'
	from /usr/lib/ruby/1.8/net/pop.rb:488:in `n_mails'
	from /usr/lib/ruby/1.8/net/pop.rb:507:in `mails'
	from /usr/lib/ruby/1.8/net/pop.rb:528:in `each_mail'
	from (irb):18
IOError: POP session not yet started
	from /usr/lib/ruby/1.8/net/pop.rb:459:in `finish'
	from (irb):19