\_ SMTP quoth Liberty Young on 3/19/2003 08:01 as having spake thusly:
\_
\_  sed -ne "s|^foobar[[:blank:]]|foo bar|p;p" processed_file

I've heard it sed that perl might be a solution:

perl -pi.bak -e 's/^foobar /foo bar/' processed_file

YMMV

David