flex 2.5.31-38ubuntu1 (amd64 binary) in ubuntu dapper

 flex is a tool for generating scanners: programs which recognized lexical
 patterns in text. flex reads the given input files for a description of a
 scanner to generate. The description is in the form of pairs of regular
 expressions and C code, called rules. flex generates as output a C source
 file, lex.yy.c, which defines a routine yylex(). This file is compiled
 and linked with the -lfl library to produce an executable. When the
 executable is run, it analyzes its input for occurrences of the regular
 expressions. Whenever it finds one, it executes the corresponding C code.
 .
 The behaviour of Flex has undergone a major change since version
 2.5.4a; Flex scanners are now reenterant, you may have multiple
 scanners in the same program with differing sets of defaults, and
 they play nicer with modern C and C++ compilers. The Flip side is
 that Flex no longer conforms to the POSIX lex behaviour, and the
 scanners require conforming implementations when flex is used in ANSI
 C mode. The package flex-old provides the older behaviour.
 .
 This product includes software developed by the University of California,
 Berkeley and its contributors. The upstream source code can be found at
 http://prdownloads.sourceforge.net/lex/flex-2.5.31.tar.bz2?download
 The project web page is at http://lex.sf.net/