#! /usr/bin/perl -w

use strict;

my @sortable;
my $inAddrRange=0;
while ( <DATA> ) {
    # are we starting an <address> range?
    $inAddrRange=1 if /<address>/;
    # are we ending a range with </address>?
    $inAddrRange=0 if m{</address>};
    # are we in the ref's AND in an addr range?
    if ($inAddrRange && /^\<ref/)
    {
        # keep track of it, but don't print it out yet.
        push @sortable, $_;
        next;
    }
    
    # else, are we done ref's?
    if (@sortable)
    {
        print for sort @sortable;
        # done with them, get rid of 'em.
        @sortable = ();
    }

    # this line can be printed out at this point.
    print;
}


__DATA__
[ same as yours, so I'm not repeating it ]