source: vendor/bash/3.1-p17/examples/functions/ksh-cd

#
# ksh-like `cd': cd [-LP] [dir [change]]
#
cd()
{
        OPTIND=1
        while getopts "LP" opt
        do
                case $opt in
                L|P)    CDOPTS="$CDOPTS -$opt" ;;
                *)      echo "$FUNCNAME: usage: $FUNCNAME [-LP] [dir] [change]" >&2
                        return 2;;
                esac
        done

        shift $(( $OPTIND - 1 ))

        case $# in
        0)      builtin cd $CDOPTS "$HOME" ;;
        1)      builtin cd $CDOPTS "$@" ;;
        2)      old="$1" new="$2"
                case "$PWD" in
                *$old*) ;;
                *)       echo "${0##*/}: $FUNCNAME: bad substitution" >&2 ; return 1 ;;
                esac

                dir=${PWD//$old/$new}

                builtin cd $CDOPTS "$dir" && echo "$PWD"

                ;;
        *)      echo "${0##*/}: $FUNCNAME: usage: $FUNCNAME [-LP] [dir] [change]" >&2
                return 2 ;;
        esac
}