From the anguish of those who try to implement the POSIX shell, I understand that edge cases are far from difficult to find. The Almquist shell (Debian Dash) is

From the anguish of those who try to implement the POSIX shell, I understand that edge cases are far from difficult to find. The Almquist shell (Debian Dash) is cited for not using lex/yacc to implement the parser, and described as untrustworthy. https://archive.fosdem.org/2018/schedule/event/code_parsing_posix_s_hell/ https://archive.fosdem.org/2018/schedule/event/code_parsing_... A major goal of this later ADA implementation is readability, in addition to (Windows) performance and ADA's safety. https://archive.fosdem.org/2019/schedule/event/ada_shell/ https://archive.fosdem.org/2019/schedule/event/ada_shell/