Regular expressions for context filter

Would you consider allowing the use of regexes to set the context 
delimiters? I am trying to set up the context filter for noweb files. 
I'm using the delimiters '>>= @', but that will break down when there is 
an at-sign in the middle of the invisible text. I'd really like to 
specify the filter like this, which more closely matches the noweb format:

start: ^<<.*>>=$
end: ^@