tech perl

my $no	= 132;	# integer
$str	= 'Hallo';	# string - single quotes

my @nos	= (1,2,3,4);	# integers
@strs	( 'apples', 'pears', 'plums');	# fruity strings

my %address	=('street' => 'Mohnweg',
	'town' => 'Suerth' );

a list is	(1,2,'fred',$a)	a seperated set of things in ( )

Scalars $

$x	= 'baa';
	='$xx';	# is string $xx
	="$no";	# is 132 -- interpolation
$y	= $x . $x;	# concatenation => baabaa
$w	=undef;

$sc	="Hallo Readers";	#notice plural
$n	=length($sc);	# 13 number of chars
$z	= chop ($x);	# ba
$z	= chomp $x);	# bad example as it will only chop
		last char if it is special ie linefeed
		$/ = \n
$a	= 'dog';
$letterD	= substr ($a, 0, 1);
case functions	uc,lc ucfirst, lcfirst

Arrays @

@ar	=(1..9);
@arr[3,4,5]	=(6,8,10);	# slice
$NumberChars	= scalar( @arr );	# also just @arr or $#arr+1
push (@arr, 'elem');		#add to end
push (@arr, @arr);		# doubles array
$end	=pop ( @arr );	# takes from end
unshift( @arr, 'begin');		# adds to beginning
$a	=shift ( @arr );	#takes from beginning
split (REG, $scalar, $limit);		# splits scalar dependent on REG
for REG =''; # empty	splits int chars
for REG=' '; # space	splits into words
join ('seperator' , @arr);		# array to scalar
splice		# look them up
reverse


Hash %	( looses order)

$bag{'green'}	= 'Sweets';
%hsh	=(k1,v1,k2,v2);	#use of list
%hsh1	=(k1=>v2, k2 => v2);
$val	= $hsh(k1);
@arr	= keys( %hsh );
@arr	= values ( %hsh );
foreach $k (keys %hsh)
while ( ($k,$v) = each %hsh )		#each is a function
delete $ENV {PATH};		# one element
undef (%hsh1 );		#deletes everything
if ( exists ($h{'key'}) )

Handles

open ( FD, "ascii.dat");
$line	=<FD>;
close (FD);		# often left to perl
open (FD,	"input.file);	# default is read
open (FD,	"> file" );	# write to file
open (FD,	">> file" );	# append
open (FD,	"process \|"	#pipe from process to here
open (FD,	"\| process");	#pipe to process

OOP version

my $fh	= new filehandle ("file" ); \|\| die;
$line	=<$fh>;
fh->close();

@lines = <FD>;		# read whole file
while ( $line = <FD>){		# read line by line
print $line; }

@arr	= <$fh>;	#whole file int array

local ($/)	= undef;
$sc	<$fh>;	# whole file into scalar

Control Structures

while ($x<10){
print $x; }
continue{
print 'something'; }

next
last

Subroutines

sub f1 {
my ($a1,a2)	= @_;	# or $a1 = shift or $_[0]
-----		# or $a2 = shift or $_[1]
return ( $f );

wantedarray()	? return @arr	: return $scalar;

my ( @arr )	= @_;	# common form

f1( \@ar1, \@ar2);		# references

sub f1 {
my ( $ar1, $ar2)	= @-;

References

$ref	= \@arr;
@$ref	=(1,2,3);
my $a	= [1,2,3,4];
my $d2	=([1,2], [3,4], [5,6] );

$h	={'one' => 12 , 'two' => 9 };

Dereferencing

$r	= \'a scalar';
print $r;	# ARRAYREF(0x12123)
	#memory location
print $$r;	# a normal scalar
$hr	= {k1 => v2};
print $hr->{k1};	# v2
	# normal hash is $h{k1}
$li	= [0,3,2];
$a	=$li->[1];	#3
$b	=$$li[1];	#3

$cr	=[1,2,3, [4,5,6] ];
print "@{$cr->[3]}"		# 4,5,6

Regular Expressions

$s	=quotemeta( '({' );	# \(\{

Namespace

$name::xx++;
$name::f1($name::xx);
or
package name
$xx++;
f1($xx);

Libraries and require

Store subroutines in name.pl
then to use
require "name.pl";
f1($xx);		# all done at run time

Modules and use

module in name.pm
package name;
---
and used as in
use name;
name::f1($x);
or
module in name/christian.pm
package name::christian
-----
and used
use name::christian
name::christian::f2($x);

module in add.pm
package add;
sub import		#special proc
my ($t,$p)	=@_;
---
activated as in
use add(2,2);		#initialisation

module name.pm
package name;
use exporter;
@ISA	=qw(Exporter);	#just learn for now
@EXPORT	=qw (True );
then name::f2($x) can be just f2($x)

Objects

package name;
sub new {
my ($type, $arg)	=@_;
my ($self)	={};
$self->{'name'}	$arg;
bless $self, $type;
}
sub destroy{
}

Package Complex;
use overload "+" => \+
sub plus{
my ($c1,$c2)	=@_;
return ( complex->new( $c1->{real} +$c2->{real}, $c1->{im} +$c2->{im}
}