my $DEBUG;
BEGIN {
   $DEBUG = $ARGV[0];
   if ($DEBUG) {
      require strict;
      import strict;
   }
}
# <-- The compiler is here because
#     Perl executes BEGIN blocks
#     as soon as it compiles them.
#     "strict" will work until the
#     end of this block (namely
#     until the end of the file).
print($test);   # strict error if $DEBUG