goto in bash (with reverse seeking)

gistfile1.sh

#!/bin/bash
# include this boilerplate
function jumpto
{
    label=$1
    cmd=$(sed -n "/#$label:/{:a;n;p;ba};" $0)
    eval "$cmd"
    exit
}
start=${1:-"start"}
jumpto $start
#start:
# your script goes here...

x=100
jumpto foo

#mid:
x=101
echo "This is not printed!"
jumpto end

#foo:
x=${x:-10}
echo x is $x

jumpto mid

#end: