echo 20000090fa173c04              | perl -lane 's/(..)/$1:/g && chop; print'

##</code><code>##

echo 20000090fa173c04              | perl -lane 's/(..)/$1:/g && chop; print lc'

##</code><code>##

echo 20000090fa173c04              | perl -lane 's/(..)/$1:/g && chop; print uc'