Flex-2.5.4a needs the following to be installed:
sh from the bash package
ar from the binutils package
as from the binutils package
ld from the binutils package
bison from the bison package
yacc from the bison package
chmod from the fileutils package
cp from the fileutils package
ln from the fileutils package
mv from the fileutils package
rm from the fileutils package
touch from the fileutils package
cc from the gcc package
egrep from the grep package
grep from the grep package
make from the make package
sed from the sed package
dirname from the sh-utils package
cat from the textutils package
tr from the textutils package