/**
 * Translate a POSIX basic regular expression to the RegExp dialect.
 *
 * grep, sed and expr read basic expressions unless told otherwise, and RegExp
 * reads something close to an extended one, so handing a pattern straight over
 * inverts every operator in it. `a+b` looks for a literal plus to grep and for a
 * repeated `a` to RegExp, and both find something, which is why this went
 * unnoticed: the failure is a wrong answer, not an error.
 *
 * Every rule below is pinned against GNU grep 3.x rather than taken from a
 * specification, because the edge cases are where the two dialects differ most:
 *
 * - `+ ? | ( ) { }` are ordinary; `\+ \? \| \( \) \{ \}` are the operators (a
 *   GNU extension for the first three).
 * - `*` is ordinary where nothing precedes it to repeat: at the start of the
 *   pattern, and after `^`, `\(` or `\|`. `^*abc` matches a literal asterisk.
 * - `^` anchors only at those same starting positions, and `$` only at the end
 *   or before `\)` / `\|`. `a^b` and `a$b` are three literal characters each.
 * - A bracket expression is copied out whole: everything inside it is already
 *   ordinary in both dialects.
 *
 * @param pattern the expression as the user typed it
 */
export declare function breToRegExp(pattern: string): string;
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