My few cents..

@arrayUnsorted=('page1.html', 'page11.html', 'page2.html', 'page3.html
+');

my @a = sort{ ($a.$b)=~/(\d*)\.htmlpage(\d*)/;$1<=>$2; } @arrayUnsorte
+d;

print "$_\n"
  foreach @a;
[download]

probably it might be better looking in the regex for /^page(\d*) ...
Best wishes