Ok I'm confused by something here...

&Search_Buff($decide == "1")
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You are using a conditional statement as an argument to the &SearchBuff subroutine. But it appears that $decide which you are testing in the conditional is defined in &Search_Buff. This will not work because the conditional is being evaluated before the subroutine is executed. It looks like you want &Search_Buff to return a boolean value, and then test that. try something like this:

if (&Search_Buff()){
     &Site_Up;
     }
else {
   &Site_Down;
     }

# Sub to search gethttpbuff.txt for a string & return 0 or 1          
sub Search_Buff
{

   # Open hethttpbuff.txt file, create an array with the data & close 
+file. End if file is locked.
   open (gethttpbuff, "gethttpbuff.txt") || die("Could not open file!"
+);
   @array = <gethttpbuff>;
   close(gethttpbuff)

   # If search string is found make var equal to "1". If the search st
+ring is not found make var equal to "0"
   foreach $line (@array) {
      if ($line =~ /$search/) {
         return 1;
      } 
   }
   return undef; # or return 0;
}
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Update: Found a logicall flaw in my code. Correcting it.