zsh script for using rvm everywhere outside of a specified directory

.zshrc

########################################
## Set up RVM excluding a custom path ##
########################################

# References:
# http://superuser.com/questions/521657/zsh-automatically-set-environment-variables-for-a-directory
# http://michael-prokop.at/blog/2009/05/30/directory-specific-shell-configuration-with-zsh/
# http://www.refining-linux.org/archives/42/ZSH-Gem-8-Hook-function-chpwd/

# Load RVM into a shell session *as a function*
[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm" 

# Custom home
CUSTOM_HOME=/custom-path/codebase

# Custom path
CUSTOM_PATH=$HOME/local/bin:$CUSTOM_HOME

function check_for_custom_path() {
    
    if [ $( echo "$PATH" | grep "$CUSTOM_PATH" ) ]
    then
        # return true
        return 0
    else
        # return false
        return 1
    fi
    
}

function source_custom_path() {
    # Set up path for custom codebase but save the default path
    OLDPATH=$PATH
    OLDGEM_HOME=$GEM_HOME
    OLDGEM_PATH=$GEM_PATH
    export PATH=$CUSTOM_PATH_PATH:$PATH
    unset GEM_HOME
    unset GEM_PATH
    
}

function unsource_custom_path() {
    # Reset to default path
    export PATH=$OLDPATH
    export GEM_HOME=$OLDGEM_HOME
    export GEM_PATH=$OLDGEM_PATH
    OLDPATH=""
    OLDGEM_HOME=""
    OLDGEM_PATH=""

}

# chpwd() is a zsh hook into changing directories.
function chpwd_custom_home() {
    
    # If this is the custom code directory and the path is not set up
    if [ "${PWD##$CUSTOM_HOME}" != "$PWD" ] && [ !$( check_for_custom_path) ]
    then 
        source_custom_path
    
    # If the path _is_ set up for the custom path and the default path, gem home, and gem path have been stored 
    elif [ check_for_custom_path ] && [ "$OLDPATH" ] && [ "$OLDGEM_PATH" ] && [ "$OLDGEM_HOME" ]
    then
        unsource_custom_path
                
    fi
}

# So then we add our function to the array of chpwd_functions.
chpwd_functions=(${chpwd_functions[@]} "chpwd_custom_home")

PATH=$PATH:$HOME/.rvm/bin # Add RVM to PATH for scripting