Abstract: A computer implemented method for parsing computer languages and structured data which converts the source language text of a computer program, e.g. C or FORTRAN, or structured data, e.g. HTML or XML, into a syntax tree. The method has two steps. The first step looks for sequences of tokens in the main token list in which no tokens referring to recursive delimiters exist. The second step parses those tokens into a partial syntax tree which is inserted back into the main token list replacing the tokens which have just been parsed. The two steps are repeated until only one token remains in the main token list. Because no recursion exists in the tokens being parsed by the second step, a find and replacement mechanism using regular expressions can be used to do the parsing. Guidelines are shown for creating a language definition using regular expressions.