Please explain the '$x ||' idiom

[goonfest]

What does the following line of code do? I've never seen it before but am now debugging somebody else's program that has this. Thanks.

$x = $x ||5;

Retitled by davido.

[Tanktalus]

$x is set to $x, unless $x is false, in which case it's set to 5. Same as $x ||= 5. Check perlop for more info.

[amw1]

Basically this reads set $x to 5 if $x is false (0 or undef)

$x = 0;
$x = $x || 5;
# prints 5
print $x;


$x = 4;
$x = $x || 5;
$prints 4
print $x;

$x = $x || 5;
# prints 5
print $x;

[Fletch]

. . . $x is false (0 or undef)

0 (but not "0 but true"), undef, or the empty string ""</nit>

[goonfest]

Okay. Thanks dudes!