Perl

1
Perl

• Functions

2
Defining Functions

• sub subroutine_name
• stmt1 stmt2
• Arguments are not listed in declaration
• May use a return statement
• If no return statement, value of last expression
  is returned
• Can return scalar, array, or hash

3
Calling Functions

• Called by
• sub_name(arg1, arg2, )
• Parens may be omitted if declaration has already
  been seen
• Arguments are available in called function as
  entries in array _at__

4
Sample Function

• sub max
• (a, b) _at__
• a gt b ? a b
• Puts args into variables
• Returns larger if they are numbers

5
Array and Hash Arguments

• Can only pass one array or hash as an argument
  unless you know the size
• Args are flattened
• (_at_a, _at_b) _at__ all in _at_a
• Can precede array or hash by a fixed number of
  scalars but
• (a, _at_b, c) _at__
• wont work

6
Scope

• my(a)
• my c, _at_e
• Declares local variable with scope of block
  (including function) or loop (in control
• Parentheses are optional

7
Strict

• use strict
• Directive requires
• Declare all variables
• Declare all functions before first use