Section for Week 5, Thursday, 2/11/99

1.  Go over LA#4 issues:
    cgi_helper:
    a) defined($title) or $title = "Page produced with CGI_Header";
    b) No indentation on the here doc's 

    counter.cgi:
    a) (! -e "filename")   (REMEMBER THE QUOTES!)
    b) print FH "0"; (no comma)
    
    environ.cgi:
    a) Get hash values in sorted key order, do:
       foreach $key (sort keys %hash) {...}

2.   Binary "<=>" returns -1, 0, or 1 depending on whether the
     left argument is numerically less than, equal to, or greater
     than the right argument.

     Binary "cmp" returns -1, 0, or 1 depending on whether the
     left argument is stringwise less than, equal to, or greater
     than the right argument.

3.  Sorting -- 
    sort BLOCK LIST	  \__  Both of these require the first argument
    sort SUBROUTINE LIST  /    to return -1,0, or 1 as LHS is less than, equal
    sort LIST		       to, or greater than RHS

    Examples:
		 # sort	lexically
		 @articles = sort @files;

		 # same	thing, but with	explicit sort routine
		 @articles = sort {$a cmp $b} @files;

		 # now case-insensitively
		 @articles = sort { uc($a) cmp uc($b)} @files;

		 # same	thing in reversed order
		 @articles = sort {$b cmp $a} @files;

		 # sort	numerically ascending
		 @articles = sort {$a <=> $b} @files;

		 # sort	numerically descending
		 @articles = sort {$b <=> $a} @files;

		 # sort	using explicit subroutine name
		 sub byage {
		     $age{$a} <=> $age{$b};  # presuming integers
		 }
		 @sortedclass =	sort byage @class;

		 # this	sorts the %age associative arrays by value
		 # instead of key using	an inline function
		 @eldest = sort	{ $age{$b} <=> $age{$a}	} keys %age;

4.  $! == the return value (errno) of the last command spawned (`...`)

5.  Using the 'g' modifier on a match will match all occurences.  In a
    scalar context, the match will iterate over the pattern.  For example,
    to match all decimal numbers in a string:
    while("4.2 5.3 5 6.4" =~ /(\d*\.?\d*)/g) {
      print "$1\n";
    }