perl is an old school language.

1. mod_perl

2. variables

   my $name = "value";
   my %hash = ( "blah"=>"foo",
                    "base"=>"path");
   print $hash{"blah"};
   
   my @array = ("a","b","c");                
   print $array[1];
   

3. comparators:
# Numerical operators:  <,  >, <=, >=, ==, !=, <=>, +, *
# String operators:    lt, gt, le, ge, eq, ne, cmp, ., x

4.

unless ($foo > 3)
   {
      print "foo";
   }
   else
   {
      print "blah";
   }

5. if, elsif,else

   $foo = 10 if ($blah == 4);

6. ?:

   $blah =  ($foo==1) ? "one":"two";
   
7. for (my $i=0;$i<10;$i++)
{
}
   foreach my $blah (@reverse)
   {
    print $blah."\n";
   }

8. keys %hash - to get keys of hash

9. next, last can be used in loops..
   equivalent to continue, and break


10. pop,
    push,
    shift,
    unshift
    splice
    join
    grep
    
11. my $rc = system "perl", "foo.pl";
     $rc >>= 8;
    print "Status Code:".$c."\n";


    my @lines = `perl foo.pl`;

    exit 37;


12. files
    my $filename= "text.txt";
    my $result = open my $handle, "<", $filename;

    if (!$result)
       {
      die "Failed to open ".$filename." because, $!;
       }

    open (my $handle, "<", $filename) || die "failed ".$!."\n";

13. while (!eof $handle)
    {
    my $line = readline $fh;
    }

14. while (my $line = readline $handle)
   {
   }

   while (my $line = <$handle>)
   {
   }

   while (<$handle>)
        {
        print $_;
     }

15. -e
    -d
    -f
    

16. regex
    
    if (  $hello =~ m/(\w+)\s+(\w)/)
         echo $1." ".$2;
    
    replace $foo =~ s/blah/foo/g;
       // g is global
       


17. modules.
    1) must return 1 in .pl file
    2) require "Demo::module_name";
         (comes from subdir Demo/module_name.pl)
    3) PERL5LIBS=blah