How to get a list of URLs from an defined bookmark's folder in Safari
After some googling and learning XPath expressions, the solution is really simple:

The following shell script - let say its name is dump_bookmarks.sh,

#!/bin/bash
for foldername
do
    /usr/libexec/PlistBuddy -x -c Print ~/Library/Safari/Bookmarks.plist | \
    xmlstarlet sel --net -t -v "//key[.='Title']/following-sibling::string[.='$foldername']/parent::node()//key[.='URLString']/following-sibling::string[1]"
    echo    #print an newline after the last entry
done


and using it as

./print_bookmarks.sh perl  #argument is the bookmark-folder name


will print a list of bookmarked URLs, like for the above screenshot will print:

https://metacpan.org/pod/Path::Tiny
http://perlmaven.com/perl-based-open-source-products
http://www.perl.com/pub/2012/04/perlunicook-standard-preamble.html
https://acidcycles.wordpress.com/2010/11/24/implementing-factories-in-perl/
http://gcstar.softonic.com/
http://steffen-wendzel.blogspot.de/p/blog-page_24.html
http://continuity.tlt42.org/


For the script you need install the xmlstarlet command, for example using Macports

sudo port install xmlstarlet