Caret lost its meaning

Hi!

Is there any way StringScanner could keep ^ meaningful? As it is, it denotes the current the beginning of the rest, but not whether we're at the start of a line.

In the following example, "bar" is not expected to be stripped.

$ cat /tmp/foo.rb
require 'strscan'

def strip(str)
  res = +''
  s = StringScanner.new(str)
  while !s.eos?
    res <<
      if s.scan(/foo/)
        ''
      elsif s.scan(/^bar/)
        ''
      else
        s.scan(/./)
        s.matched
      end
  end
  res
end

p strip('foobarbaz')

$ ruby /tmp/foo.rb
"baz"

If there's no way for StringScanner to "fix" the ^ anchor, the documentation should warn about that.
Cheers!

Start with the reproducer in /tmp/foo.rb and the StringScanner entry point used by require 'strscan'. Determine whether the ^ anchor can preserve line-start semantics during scanning; done means "bar" is not stripped from "foobarbaz", or the StringScanner documentation clearly warns about the current behavior.