The linked page lists and explains global Ruby "dollar" variables, such as:
$:
(load path)$*
(ARGV
)$?
(Last exit status)$$
(PID)$~
(MatchData
from last successful match)$~
(last MatchData
)$1 $2 $3 $4
(match groups from the last pattern match)$&
(last matched string)$+
(last match group)$'
(the string after the last matchSee this extensive list of variables Show archive.org snapshot .