I thought this would be a no-brainer. I've been using a command line version of this code explicitly entering the values to get the proper number to put into the debug_level value in nagios.cfg: perl -e 'printf("%d\n", 16|8);'. I got tired of typing it, so I wrote what i thought was a simple script: 
#!/usr/bin/perl

use strict;
use warnings;

# a simple script to produce the 'or' number required for the debug_le
+vel setting
# in nagios.cfg

my $or;
for  my $x (@ARGV){
  $or |= $x ;
}

printf("%d\n", $or);

exit;

[download]
The results were NOT what I expected. I'd have been happier if they returned '42' instead of '96', but '24' is what is supposed to come out. Here's me running it in the debugger: 

perl -d or 16 8

Loading DB routines from perl5db.pl version 1.37
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(or:9):   my $or;
  DB<53> n
main::(or:10):  for  my $x (@ARGV){
  DB<53> n
main::(or:11):    $or |= $x ;
  DB<53> x $or, $x
0  undef
1  16  
  DB<54> x $or|$x
0  16  
  DB<55> n
main::(or:11):    $or |= $x ;
  DB<55> x $or, $x
0  16  
1  8
  DB<56> x $or|$x
0  96  
  DB<57> x 16|8
0  24  
  DB<58> n
main::(or:14):  printf("%d\n", $or);
  DB<58> n
96
main::(or:16):  exit;

[download]
It's mystified the other perl programmer at my office as well. What's going on here?

In reply to Counter Intuitive Code by writch

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