http://qs1969.pair.com?node_id=303405
Description:

So you are scraping URL's out of a web page (using a CPAN module, of course), and they take all sorts of different forms: some absolute, some relative. The relative ones may or may not begin with a slash, etc.. Your job is to figure out where all of these links really go. URI::URL is your friend.

use strict;
use URI::URL;
use constant BASE => 'http://www.pair.com/pair/support/index.html';

print "BASE is ", BASE, "\n\n";

while ( chomp(my $path = <DATA>) ) {
    &tryit( $path );
}

sub tryit {
    my $relative = shift;
    my $path = URI::URL->new($relative)->abs( BASE, 1 );
    print "$relative ->\n\t$path\n\n";
}

__DATA__
http://www.pair.com
/index.html
https://www.pairnic.com/faq.m
search/
library.html

Here's the output:

BASE is http://www.pair.com/pair/support/index.html

http://www.pair.com ->
        http://www.pair.com/

/index.html ->
        http://www.pair.com/index.html

https://www.pairnic.com/faq.m ->
        https://www.pairnic.com/faq.m

search/ ->
        http://www.pair.com/pair/support/search/

library.html ->
        http://www.pair.com/pair/support/library.html