use constant MAX_VERBOSITY => 5;

BEGIN {
   my $verbosity = $ARGV[0] || 0;  # Or whatever
   my $eval = '';
   for (1..MAX_VERBOSITY) {
      my $allow = ($_ <= $verbosity) ? 1 : 0;
      $eval .= "use constant V$_ => $allow;\n";
   }
   eval $eval."1;\n" or die $@;
}

sub vprint {
   # Or whatever.
   our $msg; local *msg = \($_[0]);
   print("$msg\n");
}

vprint("msg1") if V1;  # Optimized away if arg is < 1
vprint("msg2") if V2;  # Optimized away if arg is < 2
vprint("msg3") if V3;  # Optimized away if arg is < 3
vprint("msg4") if V4;  # Optimized away if arg is < 4
vprint("msg5") if V5;  # Optimized away if arg is < 5