$str = "abcdefghijklmnopqrstuzwxyz";
$find = "efg";

if ( $str =~ m/\Q$find\E(.*)\z/s ) {
    printf "Remainder after $find is %s\n", $1;
}

my $i = index $str, $find;
if ( $i != -1 ) {
    printf "Remainder after $find is %s\n", substr $str, ($i + length($find));
}