% Erlang regular expressions lack both group capture and backreferences, thus this problem is not directly
% solvable. Presented solution is close, but not on-spec

String = "The {Quick} Brown {Fox}",
{match, FieldList} = regexp:matches(String, "\{([A-Za-z0-9_]+)\}"),

NewString = lists:foldl(fun ({Start, Length}, S) -> replstr(S, lists:reverse(string:substr(S, Start, Length)), Start) end, String, FieldList),

-module(regxdyn).
-export([start/0]).

start() ->

% Erlang regular expressions lack both group capture and backreferences, thus this problem is not directly
% solvable. Presented solution is close, but not on-spec

String = "The {Quick} Brown {Fox}",
{match, FieldList} = regexp:matches(String, "\{([A-Za-z0-9_]+)\}"),

NewString = lists:foldl(fun ({Start, Length}, S) -> replstr(S, lists:reverse(string:substr(S, Start, Length)), Start) end, String, FieldList),

io:format("~s|~s|~n", [String, NewString]).

replstr(String, ReplStr, Pos) ->
{Prefix, Suffix} = lists:split(Pos - 1, String), string:concat(string:concat(Prefix, ReplStr), string:sub_string(Suffix, length(ReplStr) + 1)).