sed -e 's/add fast \(pkg\|package\) boots-.*/add yinst pkg boots-5.0/g'
You could always avoid the OR by doing it twice
sed 's/add fast pkg boots-.*/add yinst pkg boots-5.0/g
s/add fast package boots-.*/add yinst pkg boots-5.0/g'
sed -e 's/add fast \(pkg\|package\) boots-.*/add yinst pkg boots-5.0/g'
You could always avoid the OR by doing it twice
sed 's/add fast pkg boots-.*/add yinst pkg boots-5.0/g
s/add fast package boots-.*/add yinst pkg boots-5.0/g'