Bad Programming Practices

Each post must contain one bad programming practice to add to the list. I'll start:

In C++, overload library functions by using #define. That way it looks like you are using a familiar library function where in actuality you are using something totally different.

Perl 5 is pigu disugasutingu.

Using it is a programming error.

Why is
sub proc{my @arr=('a','b','c');return @arr};print( (proc())[1] );,
possible, but not
sub proc{my %h=('a'=>'b','c'=>'d');return %h};print( (proc()){'a'} );

UNLIMITED IRRITATION WORKS