What I have found to be the easiest means of doing this is to give your submit button a name attribute like so:

<input type=submit name=in value="Format HDD">

And the browser will submit a in=Format%20HDD key-value pair to you. So upon loading you look for this key and value and if you have it you've been submitted. Pseduo-code follows.

#use CGI or whatever;
if( $param{in} eq 'Format HDD' ){
  #process form submission
  #redirect elsewhere or print status screen
}
else{
  #print form
}
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-- 
perl -p -e "s/(?:\w);(<A HREF="/index.pl?node=st&lastnode_id=3333">st<
+/A>)/'\$1/mg"
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