... After only 3 hours searching, finally found a mistake in my code ...

I am somewhat disappointed actually getting no warnings from the compiler - please consider the following code: 
#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my %hash;

$hash{'A'.'B'} = 1;
# note a mistakenly written comma between 'C' and 'D'  
$hash{'C','D'} = 2;
$hash{'E','F'} = 3;

print Dumper(\%hash);
print exists $hash{'CD'} ? "YES\n" : "NO\n";

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And here is the output 
$VAR1 = {
          'CD' => 2,
          'EF' => 3,
          'AB' => 1
        };
NO

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My xterm shows nothing between C and D in the output from Dumper, but with hexdump i could see that there is actually HEX: '1c' there 
24 56 41 52 31 20 3d 20  7b 0a 20 20 20 20 20 20  |$VAR1 = {.      |
20 20 20 20 27 43 1c 44  27 20 3d 3e 20 32 2c 0a  |    'C.D' => 2,.|
20 20 20 20 20 20 20 20  20 20 27 45 1c 46 27 20  |          'E.F' |
3d 3e 20 33 2c 0a 20 20  20 20 20 20 20 20 20 20  |=> 3,.          |
27 41 42 27 20 3d 3e 20  31 0a 20 20 20 20 20 20  |'AB' => 1.      |
20 20 7d 3b 0a 4e 4f 0a                           |  };.NO.|

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Any ideas, what's really happened? Why is it '1c' and not 'f5'? Is it a bug that perl produces no warnings in this case?

In reply to Comma Operator, BUG or feature ??? by nif

Title:
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