TOP:
my $num = <STDIN>;
if( $num != 10 and $num != 0 ) #ok, a horrible condition
{
  goto TOP;
}

#rest of code

##</code><code>##

my $input;
while( $input != "good" )
{
  print "Please enter number:\n";
  $input = <STDIN>;
}

#rest of code