use FileHandle;
my  $htmlfile = new FileHandle("XXX.html", "r") ;
while  ($line = <$htmlfile>)  { # process each line

##</code><code>##

<a class=   ---->   <div class="main-button-wrapper"><a class=   or 
<\a>        ---->   <\a><\div>
##</code><code>##

$line =~ s/<\/a>/<\/a><\/div>/;