R55 is mostly a feature release with summary bugfixes:

• Fix OS/2 search_access() and UNC path logic
• Undocument printf(1) to avoid user confusion
• Fix printf builtin -R option
• Make ${var@x}, unknown x, fail (thanks izabera)
• ${var=x} must evaluate x in scalar context (10x Martijn Dekker)
• Fixup relation between lksh and mksh, reduce delta
• Improve manpage display; add OS/2 $PATH FAQ
• Fix bugs in manpage
• Review tilde expansion, removing “odd use of KEEPASN” and introduce POSIX “declaration utility” concept; wait isn’t one
• Add \builtin utility, declaration utility forwarder
• Make $'\xz' expand to xz, not \0
• Use fixed string pooling (requires the above change in host mksh)
• POSIX declaration commands can have varassign and redirections
• Add typeset -g, replacing homegrown “global”
• Disable NOPROSPECTOFWORK, APEX is reportedly fixed now
• Display ulimit -a output with flags; improve Haiku
• Drop old let] hack, use \builtin internally
• Fix padding in Lb64encode in dot.mkshrc
• Move FAQ content to a separate, new FAQ section in the manpage
• Add new standard variable PATHSEP (‘:’, ‘;’ on OS/2)
• Fix LINENO in eval and alias
• Fix “\builtin” on OS/2
• Improve (internal) character classes code for speed
• Fix: the underscore is no drive letter
• No longer hard-disable persistent history support in lksh
• Introduce build flag -T for enabling “textmode” on OS/2 (supporting CR+LF line endings, but incompatible with mksh proper)
• Merge mksh-os2
• Permit changing $OS2_SHELL during a running shell
• Fix multibyte handling in ^R (Emacs search-history)
• Allow “typeset -p arrname[2]” to work
• Make some error messages more consistent
• Disable UTF-8 detection code for OS/2 as unrealistic
• Limit alias name chars to POSIX plus non-leading ‘-’
• Expand aliases at COMSUB parse time
• Make “typeset -f” output alias-resistent
• Permit “eval break” and “eval continue”
• Make -masm=intel safe on i386
• Disambiguate $((…)) vs. $((…)…) in “typeset -f” output
• Clarify the effect of exit and return in a subshell
• Simplify compile-time asserts and make them actually compile-time
• Fix ^O in Emacs mode if the line was modified (LP#1675842)
• Address Coverity Scan… stuff… now that it builds again
• Add test -v
• Document set -o posix/sh completely