Here is a list of all documented enum values with links to the struct/union documentation for each field:

PM_LEX_DEFAULT : pm_lex_mode
PM_LEX_EMBEXPR : pm_lex_mode
PM_LEX_EMBVAR : pm_lex_mode
PM_LEX_HEREDOC : pm_lex_mode
PM_LEX_LIST : pm_lex_mode
PM_LEX_REGEXP : pm_lex_mode
PM_LEX_STRING : pm_lex_mode
PM_STRING_CONSTANT : pm_string_t
PM_STRING_OWNED : pm_string_t
PM_STRING_SHARED : pm_string_t