$foo
$IFS
IFS=a
"$PS1"
"${PS1}"
$BASH
$BASHOPTS
$BASH_ALIASES
$BASH_ARGC
$BASH_ARGV
$BASH_CMDS
$BASH_COMPLETION_COMPAT_DIR
$BASH_LINENO
$BASH_REMATCH
$BASH_SOURCE
$BASH_VERSINFO
$BASH_VERSION
$COLORTERM
$COLUMNS
$COMP_WORDBREAKS
$DBUS_SESSION_BUS_ADDRESS
$DEFAULTS_PATH
$DESKTOP_SESSION
$DIRSTACK
$DISPLAY
$EUID
$GDMSESSION
$GDM_LANG
$GNOME_KEYRING_CONTROL
$GNOME_KEYRING_PID
$GPG_AGENT_INFO
$GROUPS
$HISTCONTROL
$HISTFILE
$HISTFILESIZE
$HISTSIZE
$HOME
$HOSTNAME
$HOSTTYPE
$IFS
$INSTANCE
$JOB
$LANG
$LANGUAGE
$LC_ADDRESS
$LC_ALL
$LC_IDENTIFICATION
$LC_MEASUREMENT
$LC_MONETARY
$LC_NAME
$LC_NUMERIC
$LC_PAPER
$LC_TELEPHONE
$LC_TIME
$LESSCLOSE
$LESSOPEN
$LINES
$LOGNAME
$LS_COLORS
$MACHTYPE
$MAILCHECK
$MANDATORY_PATH
$NO_AT_BRIDGE
$OLDPWD
$OPTERR
$OPTIND
$ORBIT_SOCKETDIR
$OSTYPE
$PAPERSIZE
$PATH
$PIPESTATUS
$PPID
$PS1
$PS2
$PS3
$PS4
$PWD
$RANDOM
$REPLY
$SECONDS
$SELINUX_INIT
$SESSION
$SESSIONTYPE
$SESSION_MANAGER
$SHELL
$SHELLOPTS
$SHLVL
$SSH_AUTH_SOCK
$TERM
$UID
$UPSTART_EVENTS
$UPSTART_INSTANCE
$UPSTART_JOB
$UPSTART_SESSION
$USER
$WINDOWID
$XAUTHORITY
$XDG_CONFIG_DIRS
$XDG_CURRENT_DESKTOP
$XDG_DATA_DIRS
$XDG_GREETER_DATA_DIR
$XDG_MENU_PREFIX
$XDG_RUNTIME_DIR
$XDG_SEAT
$XDG_SEAT_PATH
$XDG_SESSION_DESKTOP
$XDG_SESSION_ID
$XDG_SESSION_PATH
$XDG_SESSION_TYPE
$XDG_VTNR
$XMODIFIERS

----------------------------------------------------

[
	["variable", "$foo"],
	["environment", "$IFS"],
	["assign-left", [
		["environment", "IFS"]
	]],
	["operator", ["="]],
	"a\r\n",
	["string", [
		"\"",
		["environment", "$PS1"],
		"\""
	]],
	["string", [
		"\"",
		["variable", [
			"${",
			["environment", "PS1"],
			"}"
		]],
		"\""
	]],
	["environment", "$BASH"],
	["environment", "$BASHOPTS"],
	["environment", "$BASH_ALIASES"],
	["environment", "$BASH_ARGC"],
	["environment", "$BASH_ARGV"],
	["environment", "$BASH_CMDS"],
	["environment", "$BASH_COMPLETION_COMPAT_DIR"],
	["environment", "$BASH_LINENO"],
	["environment", "$BASH_REMATCH"],
	["environment", "$BASH_SOURCE"],
	["environment", "$BASH_VERSINFO"],
	["environment", "$BASH_VERSION"],
	["environment", "$COLORTERM"],
	["environment", "$COLUMNS"],
	["environment", "$COMP_WORDBREAKS"],
	["environment", "$DBUS_SESSION_BUS_ADDRESS"],
	["environment", "$DEFAULTS_PATH"],
	["environment", "$DESKTOP_SESSION"],
	["environment", "$DIRSTACK"],
	["environment", "$DISPLAY"],
	["environment", "$EUID"],
	["environment", "$GDMSESSION"],
	["environment", "$GDM_LANG"],
	["environment", "$GNOME_KEYRING_CONTROL"],
	["environment", "$GNOME_KEYRING_PID"],
	["environment", "$GPG_AGENT_INFO"],
	["environment", "$GROUPS"],
	["environment", "$HISTCONTROL"],
	["environment", "$HISTFILE"],
	["environment", "$HISTFILESIZE"],
	["environment", "$HISTSIZE"],
	["environment", "$HOME"],
	["environment", "$HOSTNAME"],
	["environment", "$HOSTTYPE"],
	["environment", "$IFS"],
	["environment", "$INSTANCE"],
	["environment", "$JOB"],
	["environment", "$LANG"],
	["environment", "$LANGUAGE"],
	["environment", "$LC_ADDRESS"],
	["environment", "$LC_ALL"],
	["environment", "$LC_IDENTIFICATION"],
	["environment", "$LC_MEASUREMENT"],
	["environment", "$LC_MONETARY"],
	["environment", "$LC_NAME"],
	["environment", "$LC_NUMERIC"],
	["environment", "$LC_PAPER"],
	["environment", "$LC_TELEPHONE"],
	["environment", "$LC_TIME"],
	["environment", "$LESSCLOSE"],
	["environment", "$LESSOPEN"],
	["environment", "$LINES"],
	["environment", "$LOGNAME"],
	["environment", "$LS_COLORS"],
	["environment", "$MACHTYPE"],
	["environment", "$MAILCHECK"],
	["environment", "$MANDATORY_PATH"],
	["environment", "$NO_AT_BRIDGE"],
	["environment", "$OLDPWD"],
	["environment", "$OPTERR"],
	["environment", "$OPTIND"],
	["environment", "$ORBIT_SOCKETDIR"],
	["environment", "$OSTYPE"],
	["environment", "$PAPERSIZE"],
	["environment", "$PATH"],
	["environment", "$PIPESTATUS"],
	["environment", "$PPID"],
	["environment", "$PS1"],
	["environment", "$PS2"],
	["environment", "$PS3"],
	["environment", "$PS4"],
	["environment", "$PWD"],
	["environment", "$RANDOM"],
	["environment", "$REPLY"],
	["environment", "$SECONDS"],
	["environment", "$SELINUX_INIT"],
	["environment", "$SESSION"],
	["environment", "$SESSIONTYPE"],
	["environment", "$SESSION_MANAGER"],
	["environment", "$SHELL"],
	["environment", "$SHELLOPTS"],
	["environment", "$SHLVL"],
	["environment", "$SSH_AUTH_SOCK"],
	["environment", "$TERM"],
	["environment", "$UID"],
	["environment", "$UPSTART_EVENTS"],
	["environment", "$UPSTART_INSTANCE"],
	["environment", "$UPSTART_JOB"],
	["environment", "$UPSTART_SESSION"],
	["environment", "$USER"],
	["environment", "$WINDOWID"],
	["environment", "$XAUTHORITY"],
	["environment", "$XDG_CONFIG_DIRS"],
	["environment", "$XDG_CURRENT_DESKTOP"],
	["environment", "$XDG_DATA_DIRS"],
	["environment", "$XDG_GREETER_DATA_DIR"],
	["environment", "$XDG_MENU_PREFIX"],
	["environment", "$XDG_RUNTIME_DIR"],
	["environment", "$XDG_SEAT"],
	["environment", "$XDG_SEAT_PATH"],
	["environment", "$XDG_SESSION_DESKTOP"],
	["environment", "$XDG_SESSION_ID"],
	["environment", "$XDG_SESSION_PATH"],
	["environment", "$XDG_SESSION_TYPE"],
	["environment", "$XDG_VTNR"],
	["environment", "$XMODIFIERS"]
]

----------------------------------------------------

Checks for environment variables.
