Convert option -region

I have not seen any examples of the -region option for convert.

I thought maybe one could do something in a specific region
and then shift that area somewhere else as an alternative to
-clone and -crop for a `cut and paste' operation.

The following successfully rotates a feature,
however the original is left in place (I was hoping the
original area may be filled with the background colour)
and I cannot see how to readily shift the feature elsewhere.

# Rotates the region about the origin of the region
# but cannot relocate the region

convert -size 300x200 xc:blue \
        -fill red \
        -draw 'rectangle 20,20 30,50' \
        -draw 'rectangle 40,70 50,80' \
        -fill lightgreen \
        -draw 'rectangle 20,50 30,80' \
        -region 20x60+20+20 -rotate "<-90" \
        -flatten \
        win:



Damien