sed question??

[bruce]

Evening..

As a test, the following is an attempt to replace "text" from a test
file with "text" from an external file.

aa=$(cat www1.txt)
sed -i "s*#\tISSUES/NOTES::*$aa*g" foo.py1

When I check the foo.py1 file, I get "$aa" in the file, instead of the
replacement text.

The test is using replacement delimeters for the sed, as the
replacement text has slashes...

thanks for any pointers.