<P> Many variations of these original forms of regular expressions were used in Unix programs at Bell Labs in the 1970s, including vi, lex, sed, AWK, and expr, and in other programs such as Emacs . Regexes were subsequently adopted by a wide range of programs, with these early forms standardized in the POSIX. 2 standard in 1992 . </P> <P> In the 1980s the more complicated regexes arose in Perl, which originally derived from a regex library written by Henry Spencer (1986), who later wrote an implementation of Advanced Regular Expressions for Tcl . The Tcl library is a hybrid NFA / DFA implementation with improved performance characteristics, earning praise from Jeffrey Friedl who said, "...it really seems quite wonderful ." Software projects that have adopted Spencer's Tcl regular expression implementation include PostgreSQL . Perl later expanded on Spencer's original library to add many new features, but has not yet caught up with Spencer's Advanced Regular Expressions implementation in terms of performance or Unicode handling . Part of the effort in the design of Perl 6 is to improve Perl's regex integration, and to increase their scope and capabilities to allow the definition of parsing expression grammars . The result is a mini-language called Perl 6 rules, which are used to define Perl 6 grammar as well as provide a tool to programmers in the language . These rules maintain existing features of Perl 5. x regexes, but also allow BNF - style definition of a recursive descent parser via sub-rules . </P> <P> The use of regexes in structured information standards for document and database modeling started in the 1960s and expanded in the 1980s when industry standards like ISO SGML (precursored by ANSI "GCA 101 - 1983") consolidated . The kernel of the structure specification language standards consists of regexes . Its use is evident in the DTD element group syntax . </P> <P> Starting in 1997, Philip Hazel developed PCRE (Perl Compatible Regular Expressions), which attempts to closely mimic Perl's regex functionality and is used by many modern tools including PHP and Apache HTTP Server . </P>

If w = t and t = 9 what is the value of w –9 –1 1 9