c:\@Work\Perl>perl -wMstrict -le
"$_ = 'a { b } c { d^ } e {{F}} {{^G}}';
 ;;
 s/\{([^{^}]+)\}/ lbracket $1 rbracket /g;
 print qq{'$_'};
"
'a  lbracket  b  rbracket  c { d^ } e { lbracket F rbracket } {{^G}}'