Cool/useful short examples of Perl?

[Matt Lawrence]

On 08/06/11 13:41, Paul Makepeace wrote:
> On Wed, Jun 8, 2011 at 13:17, Tom Hukins<tom at eborcom.com>  wrote:
>> On Wed, Jun 08, 2011 at 02:00:41PM +0200, Abigail wrote:
>>> I'd rather go for sacking people that don't know the difference
>>> between
>>>
>>>      if (something) { ... }
>>>
>>> and
>>>
>>>      unless (!something) { ... }
>> It's sunny outside and pubs are open:  I can think of worse times to
>> lose my job.
>>
>>> Or does everyone think they are always equivalent?
>> I'm not everyone, and with a language as flexible as Perl I hesitate
>> to make strong statements involving words like "always", but I don't
>> recall encountering a situation where they differ.
> $ perl -le 'print "$_ == !!$_ ? ", $_ == !!$_ ? "yes" : "no" for (-1,
> 0, 1, 2, undef)'
> -1 == !!-1 ? no
> 0 == !!0 ? yes
> 1 == !!1 ? yes
> 2 == !!2 ? no
>   == !! ? yes
>

But:

$ perl -le 'print 0 eq !!0 ? "yes" : "no"'
no

This still wouldn't affect the behaviour of the original example. In the 
context of an if or unless statement, the only thing that matters is the 
boolean value of the expression, not exactly which true or false value 
it is. Perl's canonical true and false are 1 and '' respectively, but 
everything has a boolean value.

Matt