A solution using find
:
To rename files only:
find /your/target/path/ -type f -exec rename 's/special/regular/' '{}' \;
To rename directories only:
find /your/target/path/ -type d -execdir rename 's/special/regular/' '{}' \+
To rename both files and directories:
find /your/target/path/ -execdir rename 's/special/regular/' '{}' \+