#!/bin/bash
# http://s...content-available-to-author-only...r.com/questions/892924/append-text-to-lines-between-two-patterns-every-time-they-appear-in-a-file

sed '/<code>/,\%</code>%s:$:<br/>:' <<':'
some text
some more text
<code>
some code
some more code
</code>

we are done
heros of the night
<code>
code code code
ka-ching
</code>

now finally really
done.
: