_ = x[OpNoMatch-1]
	_ = x[OpEmptyMatch-2]
	_ = x[OpLiteral-3]
	_ = x[OpCharClass-4]
	_ = x[OpAnyCharNotNL-5]
	_ = x[OpAnyChar-6]
	_ = x[OpBeginLine-7]
	_ = x[OpEndLine-8]
	_ = x[OpBeginText-9]
	_ = x[OpEndText-10]
	_ = x[OpWordBoundary-11]
	_ = x[OpNoWordBoundary-12]
	_ = x[OpCapture-13]
	_ = x[OpStar-14]
	_ = x[OpPlus-15]
	_ = x[OpQuest-16]
	_ = x[OpRepeat-17]
	_ = x[OpConcat-18]
	_ = x[OpAlternate-19]

	OpBeginLine                    // matches empty string at beginning of line
	OpEndLine                      // matches empty string at end of line
	OpBeginText                    // matches empty string at beginning of text
	OpEndText                      // matches empty string at end of text
	OpWordBoundary                 // matches word boundary `\b`
	OpNoWordBoundary               // matches word non-boundary `\B`

	OpLiteral:        "lit",
	OpCharClass:      "cc",
	OpAnyCharNotNL:   "dnl",
	OpAnyChar:        "dot",
	OpBeginLine:      "bol",
	OpEndLine:        "eol",
	OpBeginText:      "bot",
	OpEndText:        "eot",
	OpWordBoundary:   "wb",
	OpNoWordBoundary: "nwb",
	OpCapture:        "cap",
	OpStar:           "star",
	OpPlus:           "plus",
	OpQuest:          "que",
	OpRepeat:         "rep",

	case OpAnyChar:
		return c.rune(anyRune, 0)
	case OpBeginLine:
		return c.empty(EmptyBeginLine)
	case OpEndLine:
		return c.empty(EmptyEndLine)
	case OpBeginText:
		return c.empty(EmptyBeginText)
	case OpEndText:
		return c.empty(EmptyEndText)
	case OpWordBoundary:
		return c.empty(EmptyWordBoundary)
	case OpNoWordBoundary:
		return c.empty(EmptyNoWordBoundary)
	case OpCapture:
		bra := c.cap(uint32(re.Cap << 1))

	PerlX                           // allow Perl extensions
	UnicodeGroups                   // allow \p{Han}, \P{Han} for Unicode group and negation
	WasDollar                       // regexp OpEndText was $, not \z
	Simple                          // regexp contains no counted repetition

	MatchNL = ClassNL | DotNL

	Perl        = ClassNL | OneLine | PerlX | UnicodeGroups // as close to Perl as possible

		{"OpBeginLine", Const, 0},
		{"OpBeginText", Const, 0},
		{"OpCapture", Const, 0},
		{"OpCharClass", Const, 0},
		{"OpConcat", Const, 0},
		{"OpEmptyMatch", Const, 0},
		{"OpEndLine", Const, 0},
		{"OpEndText", Const, 0},
		{"OpLiteral", Const, 0},
		{"OpNoMatch", Const, 0},
		{"OpNoWordBoundary", Const, 0},
		{"OpPlus", Const, 0},
		{"OpQuest", Const, 0},
		{"OpRepeat", Const, 0},
		{"OpStar", Const, 0},

pkg regexp/syntax, const OpCharClass Op
pkg regexp/syntax, const OpConcat Op
pkg regexp/syntax, const OpEmptyMatch Op
pkg regexp/syntax, const OpEndLine Op
pkg regexp/syntax, const OpEndText Op
pkg regexp/syntax, const OpLiteral Op
pkg regexp/syntax, const OpNoMatch Op
pkg regexp/syntax, const OpNoWordBoundary Op
pkg regexp/syntax, const OpPlus Op
pkg regexp/syntax, const OpQuest Op

pkg regexp/syntax, const OpCharClass = 4
pkg regexp/syntax, const OpConcat = 18
pkg regexp/syntax, const OpEmptyMatch = 2
pkg regexp/syntax, const OpEndLine = 8
pkg regexp/syntax, const OpEndText = 10
pkg regexp/syntax, const OpLiteral = 3
pkg regexp/syntax, const OpNoMatch = 1
pkg regexp/syntax, const OpNoWordBoundary = 12
pkg regexp/syntax, const OpPlus = 15
pkg regexp/syntax, const OpQuest = 16