Scalars

# scalar variables
  $pi = 3.1415;
  undef $pi;                      # undefine variable
  $i += 1;
  ++$i;	                          # auto increment 
  $i--;
  $line .= "\n";
  $val ||= "Default";
  chop( $line = <STDIN>);         # remove "\n"
  $mode = 0755;                   # octal
  $mask = 0xff40;
  scalar( @days);                 # type cast 

# references
  $rs = \186282.42;  # reference to a constant scalar
  $rs = \$foo;       # reference to a scalar
  $bar = $$rs;       # dereference
  $bar = ${$rs};     # using a block which returns a reference

# Querying a reference
  $a = 10;
  $ra = \$a; 
  print ref( $ra);

Reserving some space for a scalar variable:

$i = " " x 320; 
print " Length " . length( $i) . "\n";