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Contents : Foreword : Ch01 : Ch02 : Ch03 : Ch04 : Ch05 : Ch06 : Ch07 : Ch08 :
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2.1. Hello World in Perl
2.2. Overview of Perl Lexical Structure, Syntax and Operators
2.3. Perl Variables
2.4. Basic Control Structures
2.5. Typical errors and pitfalls
This chapter provide a general overview of Perl. The problem here is that it's impossible to construct a very logical sequence of chapters in such a way that material of the next would be completely based on previous. So here is have something like view of Perl kingdom from a helicopter :-).
You should use Perl 5.10-5.16 documentation a reference, because there were several major changes in language constructs since 5.8.5. This book covers version 5.10.
Both Perl and C/C++ share the same basic rules and layout:
Scripts are executed sequentially, on a statement by statement basis.
Statements must be terminated by a semicolon, statements can be separated by new lines.
Blocks are delimited by braces.
Functions can be defined before or after you use them.
There are also several notable differences
Comments are "Shell-style" they start with the letter # and span till the end of the line
Variables do not need to be declared. Also they are weakly typed: the same variable can hold numeric value, string value and pointer.
Memory allocation for all the variables is automatic.
Operators are typed. So there is two comparison operators, one for strings (>eq==).
Conversion from string value to numeric value are performed automatically based of the type of the operator.
Language allow operation with undefined variables, in this case their initial value is assumed to be empty string in case of string operations and zero in case of numeric operations.
As language is interpreted statements can be constructed and executed dynamically.
"Dangling "else" problem is solved by not allowing it at all. Only block of statements is allowed after if (condition) construct.
Control structures are a little bit more flexible and a use a little bit different keywords.
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The Last but not Least
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