use File::Find;

my $old_hostname= "D25573786-2k2";
my $new_hostname = "75219";

finddepth (\&update_file , "C:\/elmPaul" );

sub update_file_dir 
{  
    if( /(.*)$old_hostname(.*)/i )# any files or directories
       {
           $orig = $File::Find::name ;
   $concat = $File::Find::dir . "\/$1$new_hostname$2";     rename($orig, $concat) || print "error can't rename $orig to $concat: $!";
         }
     -f $_ && push (@files, "$File::Find::name");
} # end of sub update_file_dir

foreach $file (@files ) 
     {  
         open (IN,"$file");
         print "\nReading from file: $file \n";
         @lines = <IN>;
         close IN;
         
        foreach (@lines)
        {
         
         if ( /(.*?)$old_hostname(.*?)/i ) 
          { 
            s/(.*?)$old_hostname(.*?)/$1$new_hostname$2/sgi;
          }  
          
        open (OUT,">$file");
        print OUT @lines; 
       }
     }