#*
  Attempting to solve the problem at rosetta code
  where one must determine if brackets [] are properly
  balanced and nested. Eg 
    [[][]] good
    [][]] wrong
    [][[[][]]] good

  I could add code to provide error messages etc.

HISTORY
  29 aug 2021 begun and working. This seems almost
  as succinct as the ANTLR code

*#

read; 
"[","]" { add "*"; push; }
[:space:] { clear; }
!"" { 
  clear; add "Sorry, only brackets [] allowed in this!\n";
  print; quit;
}
parse>
pop; pop;
"[*]*","ob*ob*" { clear; add "ob*"; push; .reparse }
pop;
"[*ob*]*" { clear; add "ob*"; push; .reparse }

(eof) { 
  "ob*" { clear; add "brackets look balanced!\n"; print; quit; }
  clear; add "brackets not balanced.\n"; print; quit;
}

push; push; push;