Ruby

Reference

{:.-one-column}

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