Perl Tricks and Tips
====================

Dumping a hash that's not a reference to a hash
-----------------------------------------------

print Dumper(%ENV); # dumps as an array
print Dumper(\%ENV); # make it a ref


Definedness Vs. True/False
--------------------------

$someKey is defined if it contains 0, "0", "" but evaluates false.



The Peppler Favorite (Debugging Web Stuff)
------------------------------------------
	eval {

	 # pesky weird code here that's giving you trouble

	}; warn "$@<br>" if $@

This gives you warnings in the web server's log on pesky code that's just
giving you a blank screen.


Determine Current Function Name (Useful for Logging Error Messages)
-------------------------------------------------------------------

$this_function = (caller(0))[3];

$caller[0] - $package
$caller[1] - $filename
$caller[2] - $line
$caller[3] - $subr - name of frame's function including package
$caller[4] - $has_args - whether has args
$caller[5] - $want_array - whether function was called list,scalar, void context

@caller = caller(0); current function
          caller(1); caller
		  caller(2); caller's caller

Globals
-------

__LINE__     - current Line #
__FILE__     - currenty file name
__PACKAGE__  - currenty package name

-------------------------------------------------------------------------
Running perl from the command line.

% man perlrun

Though the below is probably what you want to do.

       -i[extension]
            specifies that files processed by the "<>" construct are to be edited
            in-place.  It does this by renaming the input file, opening the out-
            put file by the original name, and selecting that output file as the
            default for print() statements.  The extension, if supplied, is used
            to modify the name of the old file to make a backup copy, following
            these rules:

            If no extension is supplied, no backup is made and the current file
            is overwritten.

            If the extension doesn't contain a "*", then it is appended to the
            end of the current filename as a suffix.  If the extension does con-
            tain one or more "*" characters, then each "*" is replaced with the
            current filename.  In Perl terms, you could think of this as:

                ($backup = $extension) =~ s/\*/$file_name/g;

            This allows you to add a prefix to the backup file, instead of (or in
            addition to) a suffix:

                $ perl -pi 'orig_*' -e 's/bar/baz/' fileA   # backup to 'orig_fileA'

            Or even to place backup copies of the original files into another
            directory (provided the directory already exists):

                $ perl -pi 'old/*.orig' -e 's/bar/baz/' fileA # backup to 'old/fileA.orig'

            These sets of one-liners are equivalent:

                $ perl -pi -e 's/bar/baz/' fileA            # overwrite current file
                $ perl -pi '*' -e 's/bar/baz/' fileA        # overwrite current file

                $ perl -pi '.orig' -e 's/bar/baz/' fileA    # backup to 'fileA.orig'
                $ perl -pi '*.orig' -e 's/bar/baz/' fileA   # backup to 'fileA.orig'

            From the shell, saying

                $ perl -p -i.orig -e "s/foo/bar/; ... "

            is the same as using the program:


-------------------------------------------------------------------------
De-referencing an anonymous array

my $self = { 'passes' => [ 'element1, 'element2' ] }

foreach my $element (@{$self->{passes}}) {

}



-------------------------------------------------------------------------
for (1..2) { ... }

shortcut.
for (my $i =1; $i <= 2; $i++) { .. }


-------------------------------------------------------------------------
* Include Library Path:

Include lib options in Perl.  Can be in @INC, PERL5LIB (env variable), use lib,
perl -I.