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Text::Starfish.pm and starfish - A Perl-based System for Text-Embedded Programming and Preprocessing


starfish-o=outputfile ] [ -e=initialcode ] [ -replace ] [ -mode=mode ] file...

where files usually contain some Perl code, delimited by <? and !>. To produce output to be inserted into the file, use variable $O or function echo.


(The documentation is probably not up to date.)

Starfish is a system for Perl-based text-embedded programming and preprocessing, which relies on a unifying regular expression rewriting methodology. If you know Perl and php, you probably know the basic idea: embed Perl code inside the text, execute it is some way, and interleave the output with the text. Very similar projects exist and some of them are listed in "SEE ALSO". Starfish is, however, unique in several ways. One important difference between starfish and similar programs (e.g. php) is that the output does not necessarily replace the code, but it follows the code by default. It is attempted with Starfish to provide a universal text-embedded programming language, which can be used with different types of textual files.

There are two files in this package: a module (Starfish.pm) and a small script (starfish) that provides a command-line interface to the module. The options for the script are described in subsection ""starfish_cmd list of file names and options"".

The earlier name of this module was SLePerl (Something Like ePerl), but it was changed it to starfish -- sounds better and easier to type. One option was `oyster,' but some people are thinking about using it for Perl beans, and there is a (yet another) Perl module for embedded Perl Text::Oyster, so it was not used.

The idea with the `starfish' name is: the Perl code is embedded into a text, so the text is equivalent to a shellfish containing pearls. A starfish comes by and eats the shellfish... Unlike a natural starfish, this starfish is interested in pearls and does not normally touch most of the surrounding meat.


A simple example

A simple example, after running starfish on a file containing:

     <? $O= "Hello world!" !>

we get the following output:

     <? $O= "Hello world!" !>
     Hello world!

The output will not change after running the script several times. The same effect is achieved with:

     <? echo "Hello world! !>

The function echo simply appends its parameters to the special variable $O.

Some parameters can be changed, and they vary according to style, which depends on file extension. Since the code is not stable, they are not documented, but here is a list of some of them (possibly incorrect):

 - code prefix and suffix (e.g., <? !> )
 - output prefix and suffix (e.g., \n#+\n \n#-\n )
 - code preparation (e.g., s/\\n(?:#+|%+\/\/+)/\\n/g )

HTML Examples

Example 1

If we have an HTML file, e.g., 7.html with the following content:

  <!--<? $O="This code should be replaced by this." !>-->

then after running the command

  starfish -replace -o=7out.html 7.html

the file 7out.html will contain:

  This code should be replaced by this.

The same effect would be obtained with the following line:

  <!--<? echo "This code should be replaced by this." !>-->

Output file permissions

The permissions of the output file will not be changed. But if it does not exist, then:

  starfish -replace -o=7out.html -mode=0644 7.html

makes sure it has all-readable permission.

Example 2

Input file 21.html:

  <!--<? use CGI qw/:standard/;
         echo comment('AUTOMATICALLY GENERATED - DO NOT EDIT');
  <TITLE>Some title</TITLE>
  <!--<? echo "Put this." !>-->


  <TITLE>Some title</TITLE>
  Put this.

Example from a Makefile

  LIST=first second third\
   fourth fifth

  <? echo join "\n", getmakefilelist $Star->{INFILE}, 'LIST' !>

Beside $O, $Star is another predefined variable: It refers to the Starfish object currently processing the text.

Example from a TeX file

 % <? $Star->Style('TeX') !>

 % For version 1 of a document
 % <? #$Star->addHook("\n%Begin1","\n%End1",'s/\n%+/\n/g');
 %    #$Star->addHook("\n%Begin2","\n%End2",'s/\n%*/\n%/g');
 %    #For version 2
 %    $Star->addHook("\n%Begin1","\n%End1",'s/\n%*/\n%/g');
 %    $Star->addHook("\n%Begin2","\n%End2",'s/\n%+/\n/g');
 % !>

 %Document 1

 Document 2

Example with Test/Release versions (Java)

Suppose you have a stanalone java file p.java, and you want to have two versions:

  p_t.java -- for complete code with all kinds of testing code, and
  p.java -- clean release version.


Copy p.java to p_t.java and modify p_t.java to be like:

  /** Some Java file.  */

  //<? $O = defined($Release) ?
  // "public class p {\n" :
  // "public class p_t {\n";
  public class p_t {

    public static int main(String[] args) {

      //<? $O = "    ".(defined $Release ?
      //qq[System.out.println("Test version");] :
      //qq[System.out.println("Release version");]);
      System.out.println("Release version");//-

      return 0;

In Makefile, add lines for updating p_t.java, and generating p.java (readonly, so that you do not modify it accidentally):

  p.java: p_t.java
        starfish -o=$@ -e='$$Release=1' -mode=0400 $<
  tmp.ind: p_t.java
        starfish $<
        touch tmp.ind


Note: This is a quite old part of Starfish and needs a revision. Macros are a form of code folding (related terms: holophrasting, ellusion(?)), expressed in the Starfish framework.

Starfish includes a set of macro features (primitive, but in progress). There are two modes, hidden macros and not hidden, which are indicated using variable $Star->{HideMacros}, e.g.:

  starfish -e='$Star->{HideMacros}=1' *.sfish
  starfish *.sfish

Macros are activated with:

  <? $Star->defineMacros() !>

In Java mode, a macro can be defined in this way:

  //m!define macro name

After //m!end, a newline is mandatory. After running Starfish, the definition will disapear in this place and it will be appended as an auxdefine at the end of file.

In the following way, it can be defined and expanded in the same place:

  //m!defe macro name

A macro is expanded by:

  //m!expand macro name

When macro is expanded it looks like this:

  //m!expanded macro name

Macro is expanded even in hidden mode by:

  //m!fexpand macro name

and then it is expanded into:

  //m!fexpanded macro name

Hidden macros are put at the end of file in this way:

  //auxdefine macro name

Old macro definition can be overriden by:

  //m!newdefe macro name



After executing a snippet, the contetns of this variable represent the snippet output.


More precisely, it is $::Star. $Star is the Starfish object executing the current code snipet (this). There can be a more such objects active at a time, due to executing Starfish from a starfish snippet. The name is introduced into the main namespace, which might be a questionable decision.


Name of the current input file.


Controls the number of iterations. The default value is 1, but we may want to repeat starfishing the text several times, or even until a fix-point is reached. For example, by setting the number of Loops to be at least 2, as in:

    $Star->{Loops} = 2 if $Star->{Loops}<2;

we require Starfish to proces the input in at least two iterations.


Output content of the current processing unit. For example, to use #-style line comments in the replace Starfish mode, one can make a final substitution in an HTML file:

 <!--<? $Star->{Out} =~ s/^#.*\n//mg; !>-->

It is important to have in mind that the contents of this variable is the output processed so far, so any final output processing should be done in a snippet where no new output is produced.


If option -o=* is used, then this variable contains the name of the specified output file.



The method for creation of a new Starfish object. If we are already processing within a Starfish object, we may use a shorter variant $Star->new().

The options, given as arguments, are a list of strings, which may include the following:

-infile=* Specifies the name of the input file (field INFILE). The file will not be read.

-copyhooks Copies hooks from the Star object ($::Star). This option is also available in loadinclude, getinclude, and include, from which it is passed to new. It causes the new object to have similar properties as the current Star object. It could be generalized to include any specified object, or to use the prototype object that is given to the constructor, but there does not seem to be need for this generalization. More precisely, -copyhooks copies the fields: Style, CodePreparation, LineComment, and per-component copies the array hook.


Adds a new hook. The first argument is the hook type, which is a string. The following is the list of hook types with descriptions:

regex, regex, replace

The hook type regex is followed by a regular expression and a replace argument. Whenever a regular expression is matched in text, it is ``starfished'' according to the argument replace. If the argument replace is the string ``comment'', it is treated as the comment. If the argument replace is code, it is used as the evaluation code. For example, the following source in an HTML file:

  <!--<? $Star->add_hook('regex', qr/^.section:(\w+)\s+(.*)/,
  sub { $_="<a name\"$_[2]\"><h3>$_[3]</h3</a>" }) !>-->

  line before
  .section:overview Document Overview
  line after

will produce the following output, in the replace mode:

  line before
  <a name"overview"><h3>Document Overview</h3</a>
  line after


This method is deprecated. It will be gradually replaced with add_hook, which is better defined since it includes hook type.

Adds a new hook. The method can take two or three parameters:

 ($prefix, $suffix, $evaluator)


 ($regex, $replacement)

In the case of three parameters ($prefix, $suffix, $evaluator), the parameter $prefix is the starting delimiter, $suffix is the ending delimiter, and $evaluator is the evaluator. The parameters $prefix and $suffix can either be strings, which are matched exactly, or regular expressions. An empty ending delimiter will match the end of input. The evaluator can be provided in the following ways:

special string 'default'

in which case the default Starfish evaluator is used,

special strings 'ignore' and 'echo'

'ignore' ignores the hook and produces no echo, 'echo' simply echos the contests between the delimiters.

other strings

are interpreted as code which is embedded in an evaluator by providing a local $_, $self which is the current Starfish object, $p - the prefix, and $s the suffix. After executing the code $p.$_.$s is returned, unless in the replacement mode, in which $_ is returned.

code reference (sub {...})

is interpreted as code which is embedded in an evaluator. The local $_ provides the captured string. Three arguments are also provided to the code: $p - the prefix, $_, and $s - the suffix. The result is the value of $_.

For the format with two parameters, ($regex, $replacement), currently in this mode addHook understands replacement 'comment' and code reference (e.g., sub { ... }). The replacement 'comment' will repeat the token in the non-replace mode, and remove it in the replace mode; e.i., equivalent to no echo. The regular expression is matched in the multi-line mode, so ^ and $ can be used to match beginning and ending of a line. (Caveat: Due to the way how scanner works, beginning of a line starts after the end of previously matched token.)


 $Star->addHook(qr/^#.*\n/, 'comment');


Or just last_update(), returns the date of the last update of the output.


Similar to the function starfish_cmd, but it expects already built Starfish object with properly set options. Actually, starfish_cmd calls this method after creating the object and returns the object.


Removes a hook specified by the starting delimiter $p, and the ending delimiter $s.


Removes all hooks. If no hooks are added, then after exiting the current snippet it will not be possible to detect another snippet later. A typical usage could be as follows:

    $Star->addHook('<?starfish ','?>', 'default');


Sets a particular style of the source file. Currently implemented options are: html, java, latex, makefile, perl, ps, python, TeX, and tex. If the parameter $s is not given, the stile given in $o->{STYLE} will be used if defined, otherwise it will be guessed from the file name in $o->{INFILE}. If it cannot be correctly guessed, it will be the Perl style.


include( filename and options ) -- starfish a file and echo

Reads, starfishes the file specified by file name, and echos the contents. Similar to PHP include. Uses getinclude function.

getinclude( filename and options ) -- starfish a file and return

Reads, starfishes the file specified by file name, and returns the contents (see also include to echo the content implicitly). By default, the program will not break if the file does not exist. The option -noreplace will starfish file in a non-replace mode. The default mode is replace and that is usually the mode that is needed in includes (non-replace may lead to a suprising behaviour). The option -require will cause program to croak if the file does not exist. It is similar to the PHP function require. A special function named require is not used since require is a Perl reserved word. Another interesting option is -copyhooks, for using hooks and some other relevant properties from the Star object ($::Star). This option is eventually passed to new, so you can see the constructor new for more details.

The code for get include is the following:

 sub getinclude($@) {
     my $sf = loadinclude(@_);
     return $sf->{Out};

and it can be used as a useful template for using loadinclude directly. The function loadinclude creates a Starfish object, and reads the file, however it is not digested yet, so one can modify the object before this.

loadinclude( filename and options ) -- load file and get ready to digest

The first argument is a filename. Loadinclude will interpret the options -replace, -noreplace, and -require. A Starfish object is created by passing the file name as an -infile argument, and by passing other options as arguments. The file is read and the object is returned. By default, the program will not break if the file does not exist or is not readable, but it will return undef value instead of an object. See also documentation about include, getinclude, and new.

-noreplace option will set up the Starfish object in the no-replace mode. The default mode is replace and that is usually the mode that is needed in includes. The option -require will cause program to croak if the file does not exist. An interesting option is -copyhooks, which is documented in the new method.


This function is usually called at the begining of a starfish file, in order to read local configuration. it tests whethere there exists a filed named starfish.conf in the current directory. If it does exist, it checks for the same file in the parent directory, then gran-parent directory, etc. Once the process stops, is starts executing the configuration files in the order from first ancestor down. For each file, it changes directory to the corresponding directory, and requires (in Perl style) the file in the package main.

starfish_cmd list of file names and options

The function starfish_cmd is called by the script starfish with the @ARGV list as the list of arguments. The function can also be used from Perl code to "starfish" a file, e.g.,

    starfish_cmd('somefile.txt', '-o=outfile', '-replace');

The arguments of the functions are provided in a similar fashion as argument to the command line. As a reminder, the command usage of the script starfish is:

starfish-o=outputfile ] [ -e=initialcode ] [ -replace ] [ -mode=mode ] file...

The options are described below:


specifies an output file. By default, the input file is used as the output file. If the specified output file is '-', then the output is produced to the standard output.


specifies the initial Perl code to be executed.


will cause the embedded code to be replaced with the output. WARNING: Normally used only with -o.


specifies the mode for the output file. By default, the mode of the source file is used (the first one if more outputs are accumulated using -o). If an output file is specified, and the mode is specified, then starfish will set temporarily the u+w mode of the output file in order to write to that file, if needed.

Those were the options.

appendfile filename, list

appends list elements to the file.

echo string

appends string to the special variable $).



returns the current year in string format.


Returns modification time of this file (in format of Perl time).


Returns modification date of this file (in format: Month DD, YYYY).


getfile file

grabs the content of the file into a string or a list.

getmakefilelist makefile, var

returns a list, which is a list of words assigned to the variable var; e.g.,

  FILE_LIST=file1 file2 file3\

  <? echo join "\n", getmakefilelist $Star->{INFILE}, 'FILE_LIST' !>

Embedded variables are not handled.

putfile filename, list

opens file, writes the list elements to the file, and closes it. `putfile filename' "touches" the file.

read_records string

The function takes one string argument. If it starts with 'file=' then the rest of the string is treated as a file name, which contents replaces the string in further processing. The string is translated into a list of records (hashes) and a reference to the list is returned. The records are separated by empty line, and in each line an attribute and its value are separated by the first colon (:). A line can be continued using backslash (\) at the end of line, or by starting the next line with a space or tab. Ending a line with \ effectively removes the "\\\n" string at the end of line, but "\n[ \t]" combination is replaced with "\n". Comments, starting with the hash sign (#) are allowed between records. An example is:

  name: J. Public
  phone: 000-111


If an attribute is repeated, it will be renamed to an attribute of the form att-1, att-2, etc.


Reads recursively (up the dir tree) configuration files starfish.conf.


There is a set of predefined styles for different input files: HTML (html), HTML templating style (.html.sfish), TeX (tex), Java (java), Makefile (makefile), PostScript (ps), Python (python), and Perl (perl).

HTML Style (html)

HTML Templating Style (.html.sfish)

This style is similar to the HTML style, but it is supposed to be run in the replace mode towards a target .html file, so it allows for more hooks. The character # (hash) at the beginning of a line denotes a comment.

Makefile Style (makefile)

The main code hooks are <? and >.

Interestingly, the makefile style has similar special requirements as Python. For example, in the following expansion:

 starfish: tmp
         starfish Makefile
         #<? if (-e "file.tex.sfish")
         #{ echo "\tstarfish -o=tmp/file.tex -replace file.tex.sfish" } !>
         starfish -o=tmp/file.tex -replace file.tex.sfish

it is convenient to have the embedded output indented in the same way as the embedded code.


get_verbatim_file( filename )

Specific to LaTeX mode. Reads textual file filename and returns a string ready for inclusion in a LaTeX document. It untabifies the file contests for proper representation of whitespace. The function code is basically:

    return "\\begin{verbatim}\n".
           "\\ end{verbatim}\n";

Note: There is no space betwen \\ and end{verbatim}.

htmlquote( string )

The following definition is taken from the CIPP project.

(http://aspn.activestate.com/ASPN/CodeDoc/CIPP/CIPP/Manual.html, link does not seem to be active any more)

This command quotes the content of a variable, so that it can be used inside a HTML option or <TEXTAREA> block without the danger of syntax clashes. The following conversions are done in this order:

       &  =>  &amp;
       <  =>  &lt;
       "  =>  &quot;


The script swallows the whole input file at once, so it may not work on small-memory machines and with huge files.


I'd like to thank Steve Yeago, Tony Cox, Tony Abou-Assaleh for comments, and Charles Ikeson for suggesting the include function and other comments.


 2001-2012 Vlado Keselj http://www.cs.dal.ca/~vlado
           and contributing authors:
      2007 Charles Ikeson (overhaul of test.pl)

This script is provided "as is" without expressed or implied warranty. This is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The latest version can be found at http://www.cs.dal.ca/~vlado/srcperl/.


There are several projects similar to Starfish. Some of them are text-embedded programming projects such as PHP with different programming languages, and there are similar Perl-based projects. When I was thinking about a need of a framework like this one (1998), I have found ePerl project. However, it was too heavy weight for my purposes, and it did not support the "update" mode, vs. replace mode of operation. I learned about more projects over time and they are included in the list below.

[ePerl] ePerl

This script is somewhat similar to ePerl, about which you can read at

http://www.ossp.org/pkg/tool/eperl/. It was developed by Ralf S. Engelshall in the period from 1996 to 1998.



[ePerl-h] ePerl hack by David Ljung Madison

This is a Perl script simulating the ePerl functionality, but with obviously much lower weight. It is developed by David Ljung Madison, and can be found at the URL: http://marginalhacks.com/Hacks/ePerl/

[Text::Template] Perl module Text::Template by Mark Jason Dominus.

http://search.cpan.org/~mjd/Text-Template/ Text::Template is a module with similar functionality as Starfish. An interesting similarity is that the output variable in Text::Template is called $OUT, compared to $O in Starfish.

[HTML::Mason] Perl module HTML::Mason by Jonathan Swartz, Dave Rolsky, and Ken Williams.

http://search.cpan.org/~drolsky/HTML-Mason-1.28/lib/HTML/Mason/Devel.pod The module HTML::Mason can also be seen as an embedded Perl system, but it is a larger system with the design objective being a "high-performance, dynamic web site authoring system".

[HTML::EP] Perl Module HTML::EP - a system for embedding Perl into HTML, by Jochen Wiedmann.

http://search.cpan.org/~jwied/HTML-EP-MSWin32/lib/HTML/EP.pod It seems that the module was developed in 1998-99. Provides a good CGI support, run-time support, session handling, a database server interface.

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