Table of topic groups > Front page of help pages > Help pages > 7. Help for Perl menu

7. Help for Perl menu

Topics

• Common
• Special encodings

Common

I have tried to learn WAP technology and Perl is common used CGI-language in WAP Servers. That's why I want to understand it. I have read about it from the book Inside WAP (a Finnish book), Pekka Niskanen, a worker of Acta Systems Oy (IT Press, 2000) and WWW Kehittäjän opas, Jouni Santara (Satku, 1996).

My examples base on the used books, but I have translated Finnish words into English. If you are a Finnish user of my plugins, I recommend to borrow or buy this book. If you understand only English, try to find some web pages or English books to learn principles of Perl.

This page is primary my personal help file to the Perl plugins menu, which is from the creators of HTML-Kit. I forgot some matters and I need some notes. In fact this is an additional Help for TM WML plugins menu.

Special encoding

Perl, Java and C++ share a subset of C syntax. C was first, C++ was built on top of that. Perl borrowed C and some C++ syntax and from some Unix tools (awk, sed, grep, Bourne shell). Then Java borrowed mostly C++ syntax but also some Perl syntax. Today people use PHP, which base partially on Perl. Many people regard it simler and I use it. I have among my CSS-pages a page for PHP.

I have made only some Java-servlets. Java and Perl has many divergent features, which I must list in order to remember them (they are difficult to remember and cause confusions). Here is a list of some features, which are good to remember:

• #! + path = the location of the Perl interpreter, for example #!/usr/bin/perl. This is the first row in Perl applications.
• # = a perl comment, which must be in a single row (no multi line comments like in many other languages); except it the first row, the perl interpreter pass all code after them (it is used also in arrays inside brackets to refer to the last element).
• $_ = default variable, which is not necessary to write
• @ + name = array variable like @table
• % + name = associative hash table, which is a list of name + value pairs like in this example:

  %colors = ('red', 0x00f, 'blue', 0x0xf0, 'green', 0xf00)
$colors('red') # refer to the value '0x00f'

• @ARGV = an array from the command interpreter variables
• $ENV = environment variable
• %ENV = environment hash table
• =~ = the binding operator, which return true if the lines have exactly the same like $row =~ />card/
• class_library::class = use classes from a library file.
• <> = the hook operator, which include a name like <NAME>. An example:

  open (FILE, "$_[0])
while (<FILE>)
$in_line = $_;...

• <,>, >> with hooks. Look an example:

  open (FILE, <data.txt) # open the file
open (FILE, >data.txt) # write to the file and replacing the existing data
open (FILE, >>data.txt) # write to the end of the file


• STDIN, STDOUT and STDERR are standard hooks handles.
• ^ = an anchor, which limits the searching, for example /^#/ = the searching is passed if the line begins with a # mark.
• -> = the reference operator, which refer to the properties of certain classes
• comparison operators as keywords in string operands:
  • lt = less than (<)
  • le = less than or equal (<=)
  • gt = greater than (>)
  • ge = greater than or equal (>=)
  • eq = equal (==)
  • ne = not equal (!=)
  • cmp = if the left operand is greater, then 1; if equal, then 0; if the right operand is greater, then -1 (<=>)
• . = a sign to concatenate strings that means to put together strings and string variables (in C++ and Java is used +)
• sub = subroutine, which works like in this example:

  # a definition of some sub application
sub my_sub { # no formal parameter list
# my $first_parameter=$_[0]; is according to the book
# one person said, that the following format is better:
my($first_parameter)=$_[0];" # these can be used with array tables
my($second_parameter)=$_[1];
}
# a call of some sub application
&my_sub($param1, $param2, $param3); # this the old syntax
# & is no longer required

• [$[] = the first element in an array
• [$#array] = the last element in an array
• Using query forms post method after the Perl file must add $ and using the get method ?.