Script to execute the next binary along in $PATH

next.sh

#!/bin/sh

dir=${1%/*}
bin=${1##*/}
shift

unset flag
set -f
IFS=:

for d in $PATH; do
	if [ "X$d" = "X$dir" ]; then
		flag=1
	elif [ -n "$flag" ] && [ -x "$d/$bin" ]; then
		exec "$d/$bin" "$@"
	fi
done

printf "%s: no \`%s' found beyond \`%s' in \$PATH\n" "${0##*/}" "$bin" "$dir" >&2
exit 127

Example usage:

$ cat ~/bin/ls
#!/bin/sh
exec next "$0" -1 "$@"