Something

#!/bin/bash
if [ "$1" == "on" ]
then
        xmodmap ~/.Xmodmap-svorak
        echo -e "Dvorak on"
        echo "on" > ~/.dvorak
else if [ "$1" == "off" ]
        xmodmap ~/.Xmodmap 2> /dev/null
        echo -e "Dvorak off"
        echo "off" > ~/.dvorak
else if [ "$1" == "" ]
        if [ "`cat ~/.dvorak`" == "on" ]
        then
                xmodmap ~/.Xmodmap 2> /dev/null
                echo -e "Dvorak off"
                echo "off" > ~/.dvorak
        else
                xmodmap ~/.Xmodmap-svorak
                echo -e "Dvorak on"
                echo "on" > ~/.dvorak
        fi
else
        echo -e "Not understood"
fi