The delete operator doesn't really belong in the list. It removes pairs from a hash, but on an array it only undefines the value of an element.

my @array = qw/tiger dog cat/;
delete $array[2];
print scalar @array; # Output is 2
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my @array = qw/tiger dog cat/;
delete $array[1];
print scalar @array; # Output is 3
delete $array[2];
print scalar @array; # Output is 1
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my @array = qw/tiger dog cat/;
delete $array[1];
print scalar @array; # Output is 3
splice @array, 2;
print scalar @array; # Output is 2
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on an array it only undefines the value of an element

Actually, it does a bit more than "only" undefining the value. I'm not sure how useful this behavior is, but it's not quite the same as simply setting the value to undef. Here's a code snippet that demonstrates:

$ perl -MData::Dumper -le '
    @array = (1 .. 3);
    delete $array[1];
    print Dumper \@array;
    delete $array[2];
    print Dumper \@array;'
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When run, it outputs the following:

$VAR1 = [
          1,
          undef,
          3
        ];

$VAR1 = [
          1
        ];
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We see that the first delete call does indeed appear to simply set the value to undef, but when we delete again, it demonstrates the difference.

Update: betterworld beat me to it, by a pretty large margin. That'll teach me not to reload before replying. :-)