Ruby cheatsheet

Code	Description
`$!`	latest error message
`$@`	location of error
`$_`	string last read by gets
`$.`	line number last read by interpreter
`$&`	string last matched by regexp
`$~`	the last regexp match, as an array of subexpressions
`$n`	the nth subexpression in the last match (same as `$~[n]`)
`$=`	case-insensitivity flag
`$/`	input record separator
`$\`	output record separator
`$0`	the name of the ruby script file
`$*` (or `ARGV`)	the command line arguments
`$$`	interpreter’s process ID
`$?`	exit status of last executed child process
`$-i` `$-l` `$-p` `$-v`	Command line switches
`$-v` (or `$VERBOSE`)	verbose mode