CGI::Ex::Template does all of this.

You can add arbitrary entries to the $OPERATORS table and then use the built in functions to rebuild the global qr's helping in the parsing.

The parse_expr method takes a reference to a string (which it will consume) and returns a parsed optree.

The play_expr method takes the optree and actually executes it.

The parser allows for TT2 style nested variables, function calls, number, double and single quoted strings, arrays and hashes. It also has proper precedence and associativity parsing.

The entry in the $OPERATORS table should contain the following:

   type: prefix, postfix, left, right, none, ternary, or assign (right
+)
   precedence: the relative precedence value
   symbols or names: an arrayref of symbols or operators for that oper
+ation
   function: a code ref to run when that operator is found.
[download]

It isn't entirely general as the variable names are TT2'ish - but it certainly could be used in other applications.

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.