$_                  Default variable
@_                  Default array
given               keyword in perl 5.10
say                 keyword in perl 5.10
say()               keyword in perl 5.10
$_[1]               This is element 1 of the default array @_
$name[$id]          This is element $id of the array @name
$phone{$name}       The element $name of the hash %phone
$$y                 $y is a reference to a scalar value. This expression dereferences it. See perlref
1                   A number
23.14               A number
12_345              This is the same as the number 12345 just in a more readable format
1+1                 Numerical operation
1   +1              Numerical operation
1   - 1             Numerical operation
!!                  Creating boolean context by negating the value on the right hand side twice
'' .                Forcing string context
0 +                 Forcing numeric context
$z ||= $y           Assigning default value to $z. It has the disadvantage of not allowing $z=0. Startin from 5.10 you can use //= instead of ||=
$self->editor       Calling method 'editor' on an object in the variable called $self