• It's a feature if you are writing obfu.
• It's a punishable offense if you use it anywhere else.
• It's a bug waiting to happen if you're coding under the cognitive handicap of sleep deprivation.
• It's what the C++ people love to refer to as "Undefined behavior."

It's what the C++ people love to refer to as "Undefined behavior."

Which reminds me of an amusing exchange on P5P in 2004:

In scalar context, the behaviour of sort() is undefined.

-- from perldoc -f sort

The other strawman I use is "sort in a scalar context might just play Nethack"

-- Randal L. Schwartz on P5P, June 10 2004

A patch is attached. It's incompatible with David's 'sortedness' patch, and fails if nethack is not in the user's path.

Configure should be expanded to detect rogue-like games that are available on the system, so that an appropriate one can be started if nethack is not installed.

My original goal was for sort to play nethack when called in a void context, however it appears that Perl is smart enough to optimise this instance away.

-- Paul Fenwick's response

From perlsyn:

NOTE: The behaviour of a "my" statement modified with a statement modifier conditional or loop construct (e.g. "my $x if ...") is undefined. The value of the "my" variable may be "undef", any previously assigned value, or possibly anything else. Don't rely on it. Future versions of perl might do something different from the version of perl you try it out on. Here be dragons.

See the note at the end of the Statement Modifiers section.