#!/usr/bin/zsh

case "$1" in
    "update-copyright")
        from="${2:-`date +'%Y' --date='last year'`}"
        to="${3:-`date +'%Y'`}"
        echo Updating copyright from $from to $to
        perl -pi -e "s/Copyright \d+-\K$from(, Paul Johnson)/$to\$1/" **/*(.)
        perl -pi -e "s/Copyright $from\K(, Paul Johnson)/-$to\$1/" **/*(.)
        ;;
    *)
        echo Unknown option "$1"
        ;;
esac