Publicid <-> URN conversion code in Perl

[John Cowan <jcowan@reutershealth.com>]

Here are two Perl programs to convert publicids to URNs
and URNs to publicids.  We should publish these on the
Web page as reference code, once they have been checked.
I have run all the examples in the I-D through them.

-- 
There is / one art             || John Cowan <jcowan@reutershealth.com>
no more / no less              || http://www.reutershealth.com
to do / all things             || http://www.ccil.org/~cowan
with art- / lessness           \\ -- Piet Hein
#!/usr/bin/perl -w
# Convert a "publicid" URN to an SGML/XML public identifier
# No copyright, no warranty, use as you will
# John Cowan asserts the moral right to be known as the author of this code

use strict;

while (<>) {
	chomp;

	# verify
	unless (s/^urn:publicid://) {
		warn "$_ is not a publicid URN\n";
		next;
		}

	# remap
	s/\+/ /g;
	s/:/\/\//g;
	s/;/::/g;
	s/%(..)/sprintf("%c", hex($1))/eg;
	print $_, "\n";
	}
#!/usr/bin/perl -w
# Convert an SGML/XML public identifier to an URN
# No copyright, no warranty, use as you will
# John Cowan asserts the moral right to be known as the author of this code

use strict;

while (<>) {
	# check validity
	if (/[^ \r\na-zA-Z0-9'()+,.\/:=?;!*#\@\$_%-]/) {
		warn "invalid public id: $_";
		next;
		}

	# normalize
	s/[\r\n ]+/ /g;
	s/^ //;
	s/ $//;

	# remap
	s/%/%25/g;
	s/;/%3B/g;
	s/::/;/g;
	s/:/%3A/g;
	s/\/\//:/g;
	s/\//%2F/g;
	s/\+/%2B/g;
	s/ /+/g;
	s/'/%27/g;
	s/\?/%3F/g;
	s/#/%23/g;

	# output
	print "urn:publicid:", $_, "\n";
	}