File::Path

Quote

remove_tree( $dir1, $dir2, ...., \%opts )

(...)

The following keys are recognised in the option hash:keep_root => $bool

When set to a true value, will cause all files and subdirectories to be removed, except the initially specified directories. This comes in handy when cleaning out an application's scratch directory.
remove_tree( '/tmp', {keep_root => 1} );