"This change modifies Go to ___________"
  + Lowercase verb after the colon
  + No trailing period
  + Keep the title as short as possible. ideally under 76 characters or shorter
+ No Markdown
+ The first PR comment (this one) is wrapped at 76 characters, unless it's
  really needed (ASCII art, table, or long link)
+ If there is a corresponding issue, add either `Fixes #1234` or `Updates #1234`

pkg regexp/syntax, const EmptyWordBoundary = 16
pkg regexp/syntax, const ErrInternalError = "regexp/syntax: internal error"
pkg regexp/syntax, const ErrInvalidCharClass = "invalid character class"
pkg regexp/syntax, const ErrInvalidCharRange = "invalid character class range"
pkg regexp/syntax, const ErrInvalidEscape = "invalid escape sequence"
pkg regexp/syntax, const ErrInvalidNamedCapture = "invalid named capture"