This document provides an overview of key Perl concepts including scalars, arrays, hashes, I/O, operators, and control structures. It discusses scalar data types like strings and numbers. It also covers arrays, hashes, and common functions for each. The document outlines I/O with the console, files, and handles. It briefly summarizes operators and precedence. Finally, it discusses control structures like if/else, loops, and modifiers.

1. * Before we start...
$ perldoc
#!/usr/bin/perl
use strict;
* Datos y Operadores
* Datos Escalares
* Strings
Datos de texto o binarios, sin significado para el programa, delimitados típicamente por comillas sencillas o dobles:
my $world = 'Mundo';
my $escaped = 'Dan O'Bannon';
my $backslash = '';
* Comillas dobles
my $newline = "n";
my $tab = "t";
my $input = "hellonworld!";
my $data = "08029t25";
my $data = "08029,"Eixample Esquerra"";
my $data = qq{08029,"Eixample Esquerra"};
* Interpolación
my $hello = "Hola, $world!n";
my $hello = qq{Hola, "$world"!n};
* Funciones típicas de cadena
length EXPR
substr EXPR,OFFSET,LENGTH,REPLACEMENT
substr EXPR,OFFSET,LENGTH
substr EXPR,OFFSET
index STR,SUBSTR,POSITION
index STR,SUBSTR
Functions for SCALARs or strings
"chomp", "chop", "chr", "crypt", "hex", "index", "lc", "lcfirst",
"length", "oct", "ord", "pack", "q//", "qq//", "reverse", "rindex",
"sprintf", "substr", "tr///", "uc", "ucfirst", "y///"
=> Más cuando hablemos de expresiones regulares
* Números
$ perldoc perlnumber
$n = 1234; # decimal integer
$n = 0b1110011; # binary integer
$n = 01234; # *octal* integer
$n = 0x1234; # hexadecimal integer
$n = 12.34e−56; # exponential notation
$n = "−12.34e56"; # number specified as a string
$n = "1234"; # number specified as a string
* Hashes, Listas y Arreglos
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2. @ Arreglo
my @author;
$author[0] = 'Asimov';
$author[1] = 'Bear';
$author[2] = 'King';
print "First author is " . $author[0] . "n";
print "Last author is " . $author[$#author] . "n";
print "Last author is " . $author[-1] . "n";
print "There are " . @author . " authorsn";
my @num = (0..10);
my @a = (@b,@c);
* Funciones típicas para arreglos
sort SUBNAME LIST
sort BLOCK LIST
sort LIST
grep BLOCK LIST
grep EXPR,LIST
join EXPR,LIST
split /PATTERN/,EXPR,LIMIT
split /PATTERN/,EXPR
split /PATTERN/
# ++$learn
$ perldoc List::Util
% Hash
my %name;
$name{'Asimov'} = 'Isaac';
$name{'Bear'} = 'Greg';
$name{'King'} = 'Stephen';
* Funciones típicas para hashes
keys HASH
values HASH
print "Authors are ".keys(%name)."n";
* Identificadores, variables y su notación
Notación
Las variables son precedidas de un sigil que indica el tipo de valor de la variable:
$ Escalar
@ Arreglo
% Hash
e.g.
my($nombre, @nombre, %nombre);
Para acceder el elemento de un arreglo o hash, se utiliza el sigil escalar:
$nombre{$id} = 'Ann';
$nombre[$pos] = 'Ben';
Es posible acceder múltiples valores al mismo tiempo utilizando el sigil de arreglo:
@nombre{@keys} = @values;
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3. @suspendidos = @nombre[@selected];
@authors =("Asimov","Bear","King");
@authors = qw(Asimov Bear King);
Variables especiales
$ perldoc perlvar
$ perldoc English
@ARGV
@INC
%ENV
%SIG
$@
@_
$_
* I/O
* Consola
STDIN
STDOUT
STDERR
e.g.
print STDERR "This is a debug messagen";
#!/usr/bin/perl
use strict;
use Chatbot::Eliza;
my $eliza = Chatbot::Eliza->new();
while(<STDIN>) {
chomp;
print "> ".$eliza->transform($_),"n";
}
* Ficheros
$ perldoc -f open
$ perldoc perlopentut
#
# Reading from a file
#
# Please don't do this!
open(FILE,"<$file");
# Do *this* instead
open my $fh, '<', 'filename' or die "Cannot read '$filename': $!n";
while (<$fh>) {
chomp; say "Read a line '$_'";
}
#
# Writing to a file
#
use autodie;
open my $out_fh, '>', 'output_file.txt';
print $out_fh "Here's a line of textn";
say $out_fh "... and here's another";
close $out_fh;
# $fh->autoflush( 1 );
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4. #
# There's much more!
# :mmap, :utf8, :crlf, ...
#
open($fh, ">:utf8", "data.utf");
print $fh $out;
close($fh);
# ++$learn
$ perldoc perlio
$ perldoc IO::Handle
$ perldoc IO::File
* Operadores y su precedencia
( y su asociatividad ( y su arity ( y su fixity ) ) )
$ perldoc perlop
left terms and list operators (leftward)
left −>
nonassoc ++ −−
right **
right ! ~ and unary + and −
left =~ !~
left * / % x
left + − .
left << >>
nonassoc named unary operators
nonassoc < > <= >= lt gt le ge
nonassoc == != <=> eq ne cmp ~~
left &
left | ^
left &&
left || //
nonassoc .. ...
right ?:
right = += −= *= etc.
left , =>
nonassoc list operators (rightward)
right not
left and
left or xor
=> Atencion!
print ( ($foo & 255) + 1, "n");
print ++$foo;
* Operadores
* Numericos
* String
* Logicos
* Bitwise
* Especiales
* Estructuras de Control
if (EXPR) BLOCK
if (EXPR) BLOCK else BLOCK
if (EXPR) BLOCK elsif (EXPR) BLOCK ... else BLOCK
LABEL while (EXPR) BLOCK
LABEL while (EXPR) BLOCK continue BLOCK
LABEL until (EXPR) BLOCK
LABEL until (EXPR) BLOCK continue BLOCK
LABEL for (EXPR; EXPR; EXPR) BLOCK
LABEL foreach VAR (LIST) BLOCK
LABEL foreach VAR (LIST) BLOCK continue BLOCK
LABEL BLOCK continue BLOCK
e.g.
for(my $i=0; $i<@author; ++$i) {
print $i.": ".$author[$i]."n";
}
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5. for(0..$#author) {
print $_.": ".$author[$_]."n";
}
foreach my $i (0..$#author) {
print $i.": ".$author[$i]."n";
}
for(0..1000000) {
print $_,"n";
}
while(<$fh>) {
# Skip comments
next if /^#/;
...
}
* Modificadores
if EXPR
unless EXPR
while EXPR
until EXPR
foreach LIST
e.g.
print "Value is $valn" if $debug;
print $i++ while $i <= 10;
Contexto
* Void
find_chores();
* Lista
my @all_results = find_chores();
my ($single_element) = find_chores();
process_list_of_results( find_chores() );
my ($self,@args) = @_;
* Escalar
print "Hay ".@author." autoresn";
print "Hay ".scalar(@author)." autoresn";
# ++$learn
$ perldoc -f wantarray
* Numerico
my $a = "a";
my $b = "b";
print "a is equal to b " if ($a==$b); # Really?
print "a is equal to b " if ($a eq $b);
* Cadena
my $a = 2;
print "The number is ".$a."n";
* Booleano
my $a = 0;
print "a is truen" if $a;
$a = 1;
print "a is truen" if $a;
$a = "a";
print "a is truen" if $a;
my $numeric_x = 0 + $x; # forces numeric context
my $stringy_x = '' . $x; # forces string context
my $boolean_x = !!$x; # forces boolean context
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