while (<MYFILE>)
{
   $line = $_;              

   if( $line =~ m/(?<!$pre)$searchTerm(?!$post)/ )
	   {print $line};       
 
}    

##</code><code>##

while (<MYFILE>)
{
   $line = $_;              

   if( $line =~ m/(?<!$pre)$searchTerm(?!$post)/ )
	   {print $line};       
  
	if ($pre = "" and $post = "") 
	{
		print "Case 1";
	} elsif ($pre = "") 
	{
		print "Case 2";  
	} elsif ($post = "") 
	{
		print "Case 3";  
	} else 
	{
		print "Case 4";  
	}                      
	print "\n";
}