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Summary of Perl Documentation

Overview

Perl is a high-level, general-purpose, and interpreted programming language known for its powerful text-processing capabilities. It is widely used for system administration, web development, and network programming.

Key Features

  • Dynamic Typing: No need to declare variable types explicitly.
  • Rich Text Processing: Built-in support for regular expressions.
  • Cross-Platform: Runs on various operating systems.
  • CPAN: Comprehensive Perl Archive Network offers thousands of reusable modules.
  • Scripting and Automation: Ideal for automating tasks and quick prototyping.

Core Concepts

Variables

  • Scalar: Stores a single value (string, number, or reference). 
    my $name = "Perl";
  • Array: Ordered list of values. 
    my @colors = ("red", "green", "blue");
  • Hash: Key-value pairs. 
    my %ages = ("Alice" => 30, "Bob" => 25);

Contexts

  • Perl evaluates expressions in scalar or list context: 
    my $count = @colors; # Scalar context: Number of elements
my @list = @colors;  # List context: All elements

Operators

  • Arithmetic: +, -, *, /, %, **
  • String: . (concatenation), x (repetition)
  • Comparison:
    • Numbers: ==, !=, <, >, <=, >=
    • Strings: eq, ne, lt, gt, le, ge
  • Regular Expressions:
    • Match: =~ /pattern/
    • Negated Match: !~ /pattern/

Control Flow

Conditionals

if ($age > 18) {
    print "Adult\n";
} elsif ($age > 12) {
    print "Teenager\n";
} else {
    print "Child\n";
}

Loops

  • For Loop: 
    for my $color (@colors) {
    print "$color\n";
}
  • While Loop: 
    while ($age < 30) {
    $age++;
}

Subroutines

  • Define reusable code blocks: 
    sub greet {
    my $name = shift;
    return "Hello, $name!";
}
print greet("Alice");

Regular Expressions

  • Perl excels at text manipulation: 
    my $string = "Hello World";
if ($string =~ /World/) {
    print "Match found!\n";
}
$string =~ s/World/Perl/; # Substitution

File Handling

  • Reading a File: 
    open(my $fh, "<", "file.txt") or die "Cannot open file: $!";
while (my $line = <$fh>) {
    print $line;
}
close($fh);
  • Writing to a File: 
    open(my $fh, ">", "file.txt") or die "Cannot write to file: $!";
print $fh "Hello, Perl!\n";
close($fh);

Modules and Packages

  • Import modules using use: 
    use strict;
use warnings;
use Math::Complex;
  • Create reusable modules: 
    package MyModule;
sub hello {
    return "Hello, Perl!";
}
1;

Debugging

  • Run scripts with debugging enabled: 
    perl -d script.pl
  • Use warn and die for error messages: 
    warn "This is a warning\n";
die "This is a fatal error\n";

Best Practices

  • Use use strict; and use warnings; to catch errors.
  • Use meaningful variable names and proper indentation.
  • Leverage CPAN modules for reusable functionality.

Resources

Perl is a versatile and robust language with extensive support for text processing and automation tasks, making it a valuable tool for developers and system administrators.