Errata

The "Expression" in the fifth line is the same as the fourth, but based on the Value should instead be:

"'$dave'"

Which is to say add surrounding double quotes around the existing single quoted variable.

I couldn't get the directory stack system to work as advertised. Here's a variation
of the source that does work (this is a section from my .kshrc):

# should this be in this file?
export DIRSTACK="" # [CHANGE 1/3] THERE IS NO REASON TO
# HAVE STACK NON-EMPTY TO START WITH.

function dirs {
print $DIRSTACK
}

function getNdirs {
stackfront=''
let count=0
while (( count < $1 )); do
stackfront="$stackfront ${DIRSTACK%% *}"
DIRSTACK=${DIRSTACK#* }
let count++
done
}

function pushd {
if [[ $1 == ++([0-9]) ]]; then
# case of pushd +n: rotate n-th directory to top
num=${1#+}
getNdirs $num

newtop=${stackfront##* }
stackfront=${stackfront%$newtop}

DIRSTACK="$newtop $stackfront $DIRSTACK"
cd $newtop

elif [[ -z $1 ]]; then
# case of pushd without args; swap top two directories
firstdir=${DIRSTACK%% *}
DIRSTACK=${DIRSTACK#* }
seconddir=${DIRSTACK%% }
DIRSTACK=${DIRSTACK#* }
DIRSTACK="$seconddir $firstdir $DIRSTACK"
cd $seconddir

else
# normal case of pushd dirname
dirname=$1
if [[ -d $dirname && -x $dirname ]]; then
bufpwd=$PWD # [CHANGE 2/3]: this is a new line
cd $dirname
DIRSTACK="$bufpwd $DIRSTACK" # [CHANGE 3/3]: changed
#print "$DIRSTACK"
else
print still in "$PWD."
return 1
fi
fi
}

function popd { # pop directory off the stack, cd to new top
if [[ $1 == ++([0-9]) ]]; then
# case of oppd +n : delete n-th directory from stack
num=${1#+}
getNdirs $num
stackfront=${stackfront% *}
DIRSTACK="$stackfront $DIRSTACK"

else
# normal case of popd without arg
if [[ -n $DIRSTACK ]]; then
top=${DIRSTACK%% *}
DIRSTACK=${DIRSTACK#* }
cd $top
print "$PWD"
else
print "stack empty"
return 1
fi
fi
}