Control Structures

Statement Blocks

• Control Structures are constructs used to control the flow of program execution.
• A control structure is generally associated with a statement block.
• A statement block is a sequence of statements, starting and ending with curly braces.
• A block of statements is allowed in place of any single statement (but the reverse is not generally true, e.g. no dangling else statements).
• The final semicolon in a block of statements is optional, allowing you to use sane C form, or confuse the heck out of everyone by using the pascal form.
• Example:
  

  { 
      some_statement; 
      some_statement; 
      some_statement; 
  } 
  

• In perl, truth is defined as follows:

  Table to Truth for Perl

  Element	Truth
  0, "0", or anything that computes to 0 or "0"	False
  undef, or anything that computes to undef	False
  "", or anything that computes to ""	False
  Everything Else	True
  "00" (string of two zeros)	True (it is not a single 0 after all)
  "0.0"	True (again, it is not a single 0 after all)