postfix to infix by tails

s"\w"{&_}"g
:
s"\([^{}]*\)\([+-]}[*/-]\|[*/]}/\)"(\1)\2"
s"\([^{}]*\)\([+-]}{[^}]*}[*/]\)"(\1)\2"
s".}{\([^}]*\).}\([^{]\)"\2\1\2}"
t
s"{\|.}""g

Note that non-ascii characters in the above source code will be escaped (such as \x9f).

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