First try wrapping your sample code in code tags to make it readable, so it looks like this:

foreach $x (@x) {  
   open ($x, ">>$log") or die;  
   print while (<$x>);  
   printf "%7d",$x; 
}  

close ($x);
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A more common idiom for printing to a file would be this:

open (OUTPUT, ">>$log") or die "Error opening file $log ($!)\n";
my $line = join ' ', @x;
print OUTPUT $line, "\n";
close (OUTPUT) or die "Error closing file $log ($!)\n";
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Catching possible errors from your system IO operations in $! is generally a good practice. Also, the version I showed doesn't reopen the filehandle every time you want to print a array element to the file. The join operator is very useful, do a perldoc -f join if you've never seen it before. A perldoc -f open would probably be helpful to you as well.

Hope that this helps. :)