$!
latesterror message
$@
locationof error
$_
stringlast read by gets
$.
linenumber last read by interpreter
$&
stringlast matched by regexp
$~
thelast regexp match, as an array of subexpressions
$n
thenth subexpression in the last match (same as $~[n])
$=
case-insensitivityflag
$/
inputrecord separator
$\
outputrecord separator
$0
thename of the ruby script file
$thecommand line arguments
$$
interpreter’sprocess ID
$?
exit status of last executed child process