Introduction

Perl's pretty fast for an interpreter. Sure, its slower than an equivalent C++ program, but I'd put it up against VB any day.

The Perl development environment is command line driven, with source files being plain text. I view it as a refreshing change from "GUIs" which are so easy to develop, but so hard to figure out six months later. Also, since source is pure text, there's less chance of file corruption trashing your source code.

Perl has no GUI user interface. It's pure STDIN/STDOUT/STDERR plus UNIX like file streams. For quick reports, file integrety checking, system administration or file conversion, this is exactly what you want. If you need a GUI user interface, simply add your favorite Web Browser and an HTML form.

Perl is perfect for small to medium text based "web apps". It develops ultra-quick, runs ultra-quick, and can handle small to medium database requirements. And it's totally portable. To change servers or ISP's, just FTP the site over and change the line saying where the Perl interpreter is.

Perl isn't the answer to everything. You certainly wouldn't create a draw or paint program in Perl. If run-time speed is critical, Perl isn't the answer. You probably can't directly hit your corporate database with Perl (although with new support being added all the time, this too may change). And Perl is "corporationally incorrect". There's no drag and drop. All source is text. It's free. And it's not made in Redmond.

I like Perl. A lot.

Where Perl Excels

• Impossible Deadlines
• Batch File and Shellscript Substitutes
• Parsing
• Quick and Dirty Reports, and Error Checking
• File Conversions

Impossible Deadlines

Assignment:

Perl Solution:

Subroutine 1:

Subroutine 2:

Subroutine 3:

Batch File and Shellscript Substitutes

Assignment:

Perl Solution:

Subroutine 1:

Subroutine 2:

Subroutine 3:

Subroutine 4:

Parsing

Assignment:

Perl Solution :-)

• Open input (disk report) and output files.
• while(<INPUT_REPORT>)      #pseudo code, not exact
• Read next line
• Use regular expression to filter out JCL.
• Use regular expression to deduce whether line is new record, or just word wrap
• On new record
• finish old record
• write old record
• zero totals
• start new record
• Using regular expressions, parse the data from the prose and update all totals.
• Close input and output files.

Quick and Dirty Reports, and Error Checking

Assignment:

Perl Solution:

Subroutine 1: Deduce totals from individual timesheet files:

Subroutine do_one_file:

Subroutine 2: Deduce totals from intermediate file imported by database:

Subroutine 3: Print the results:

File Conversions

Perl Hints and Landmines

Don't change directories

Readdir() bugs on other drives

Weak Type Checking

Variables are Global by Default

sub getName
 {
 $name = <STDIN>;
 chomp($name);
 return($name);
 }

sub doLabel
 {
 print "What is your name?==>";
 $name = $getName();
 print "\nWhat is your spouses name?==>";
 $spousename = $getName();
 print "\n";
 print PRINTERDEVICE "Hi. I'm $name.\n";
 print PRINTERDEVICE "My spouse is $spousename.\n";
 }

 $name = <STDIN>;

 my($name) = <STDIN>;

---

NOTE: I've seen rare and intermittent cases where variables constructed as my($varname) = expression act funny in loops. If you find something like that, declare the var on one line and assign it in the next as follows:

 my($name);
 $name = <STDIN>;

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