use constant MAX_VERBOSITY => 5;

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

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

vprint1("msg1");  # Optimized away if arg is < 1
vprint2("msg2");  # Optimized away if arg is < 2
vprint3("msg3");  # Optimized away if arg is < 3
vprint4("msg4");  # Optimized away if arg is < 4
vprint5("msg5");  # Optimized away if arg is < 5