This can be done with a one liner, but to give you an idea how this works you can move the web page to a back up, read it in line by line and just substitute the old address with the new address. For this example I will assume your html fuile is called index.html.

** Warning Unested Code **

open OUT, "> index.html" or die "$!"; # open the new HTML file
open IN, "index.html.old" or die "$!"; open the old HTML file to be re
+ad in
while (<IN>) {
       s/@xyz\.com/@xyzabc\.com/g; #for every line that has @xyz.com r
+eplace it with @xyzabc.com
       print OUT; # print the line into the new HTML file
}
close IN or warn "$!"; # close the old file
close OUT or warn "$!"; # close the new file
[download]

That should do it.

- Prime