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Printing with Here Documents
Printing with "here documents"
- Unfortunately, much of what your CGI
applications will be sending to the Web browser will include the
double-quote mark. It becomes tedious, especially for long blocks
of HTML code, to make print statements for every line of HTML and
to escape every occurrence of a double-quote with a backslash.
Consider the following table definition:
#!/usr/local/bin/perl
print "Content-type: text/html\n\n";
print "<TABLE BORDER = \"1\" CELLPADDING =
\"2\" CELLSPACING = \"2\">";
print "<TR>";
print "<TD ALIGN = \"center\">Email</TD>";
print "<TD ALIGN = \"center\"> <A HREF =
\"mailto:selena\@foobar.com\">selena\@foobar.com<</A></TD>";
print "</TR>";
print "</TABLE>";
- If any one of those backslashes are
missing, the whole script breaks down. And this is a very small
block of code!
- One solution to the sending of large
blocks of HTML code which incorporate the double-quote is to use
the "here document" method of printing. The "here document"
method tells Perl to print everything within a certain block of
boundaried code. The "here document" uses the generic
format:
print <<[TEXT_BOUNDARY_MARKER];
[Text to be printed]
[TEXT_BOUNDARY_MARKER]
- For example, this code will print out
the basic HTML header:
#!/usr/local/bin/perl
print <<end_of_html_header;
Content-type: text/html\n\n
<HTML>
<HEAD>
<TITLE>My Title</TITLE>
</HEAD>
<BODY>
</BODY>
</HTML>
end_of_html_header
- In short, the "here document" method of
printing tells the Perl interpreter to print out everything it
sees (print <<) from the print line until it finds the text
boundary marker specified in the print line (end_of_html_header).
The text boundary marker can be anything you like of course, but
it is useful to make the flag descriptive.
- Further, the ending flag must be
"exactly" the same as the flag definition. Thus, the following
code will fail because the final flag is not indented
correctly:
print <<" end_of_header";
<HTML><HEAD>
<TITLE>$title</TITLE>
</HEAD><BODY></BODY></HTML>
end_of_header
- The final "end_of_header" tag should
have been indented four spaces, but it was not indented at
all.
Printing with Perl
Table of Contents
Using qq
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