Cool/useful short examples of Perl?

[Kaoru]

On Wed, Jun 8, 2011 at 1:41 PM, Paul Makepeace <paulm at paulm.com> wrote:
> $ perl -le 'print "$_ == !!$_ ? ", $_ == !!$_ ? "yes" : "no" for (-1,
> 0, 1, 2, undef)'
> -1 == !!-1 ? no
> 0 == !!0 ? yes
> 1 == !!1 ? yes
> 2 == !!2 ? no
>  == !! ? yes

Whether they are equal according to "==" shouldn't matter here, should
it? What matters between if(something) and unless (!something) is
whether something and !!something are the same boolean-wise.

I think this code shows they are all the same?


$ perl -le 'print "$_\tis the same booleanwise as\t!!$_\t", !($_ xor
!!$_) ? "yes" : "no" for (-1, 0, 1, 2, undef)'
-1      is the same booleanwise as      !!-1    yes
0       is the same booleanwise as      !!0     yes
1       is the same booleanwise as      !!1     yes
2       is the same booleanwise as      !!2     yes
        is the same booleanwise as      !!      yes

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As has been pointed out "!" can be overridden etc, but I think the use
of unless is safer than your example suggested.

- Alex