| How to Embed Perl Code in HTML Documents |
Perl code can be embedded in three ways:
| 1.) [- ... -] Execute code | top |
[- $a = 5 -] [- $b = 6 if ($a == 5) -] The code between the [- and the -] is executed. No output will be
generated in the HTML. This is mainly for assignments, function calls,
database queries, etc.
| 2.) [+ ... +] Output the result | top |
[+ $a +] [+ $array[$b] +] [+ "A is $a" +] The code between the [+ and the +] is executed and the return
value (the value of the last expression evaluated) is output (sent
to the browser in the HTML stream).
| 3.) [! ... !] Execute code once | top |
[! sub foo { my ($a, $b) = @_ ; $a * $b + 7 } !]Same as [- ... -], but the code is only executed for the first
request. This is mainly for function definitions and one-time
initialization.
Embperl support some meta commands to control the "program flow"
within the Embperl document. This can be compared to preprocessor
commands in C. The meta commands take the following form: [$ <cmd> <arg> $]  | if, elsif, else, endif | | | The if command is just the same as in Perl. It is used to
conditionally output/process parts of the document.
Example: [$ if $ENV{REQUEST_METHOD} eq 'GET' $]
This is a GET request
[$ elsif $ENV{REQUEST_METHOD} eq 'POST' $]
This is a POST request
[$ else $]
This is not GET and not POST
[$ endif $]This will output one of the three lines depending on the setting
of $ENV{REQUEST_METHOD}. |  | | | while, endwhile | | | The while command can be used to create a loop in the HTML
document. For example: [$ while ($k, $v) = each (%ENV) $]
[+ $k +] = [+ $v +] <BR>
[$ endwhile $]The above example will display all environment variables, each
terminated with a line break. | | | | do, until | | | The do until also create a loop, but with a condition at the end.
For example: [- @arr = (3, 5, 7); $i = 0 -]
[$ do $]
[+ $arr[ $i++ ] +]
[$ until $i > $#arr $] | | | | foreach, endforeach | | | Create a loop iterating over every element of an array/list.
Example: [$ foreach $v (1..10) $]
[+ $v +]
[$ endforeach $] | | | | var <var1> <var2> ... | | | By default, you do not need to declare any variables you use within an
Embperl page. Embperl takes care of deleting them at the end of each
request. Sometimes, though, you want to declare them explicitly. You
can do this by using var: [$ var $a @b %c $] Has the same effect as the Perl code: use strict ;use vars qw {$a @b %c} ; | | | | hidden | | | hidden is used for creating hidden form fields and is described in
the form field section below. | |
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