hi. 

here is a session in irb:
irb(main):001:0> 10.power!(200)
NoMethodError: undefined method `power!' for 10:Fixnum
        from (irb):1
irb(main):002:0> help Fixnum
=> nil
irb(main):003:0> 10.power!(200)
=> 
100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
irb(main):004:0> quit

so a call to help Fixnum makes the power! method to be available ? 

i use slackare 10.2 with a self-made package of ruby 1.8.4 compiled with 
CFLAGS="-O2 -march=$arch -mcpu=i686" \
CXXFLAGS="-O2 -march=$arch -mcpu=i686"\
./configure --prefix=/usr --enable-shared
make
make install DESTDIR=$pkg
make install-doc DESTDIR=$pkg

on an Athlon XP 1800+ 

# note: 
not all people on #ruby-lang on irc.freenode.net got that error