Scalar variable reference

Perl
Reference
here

A scalar variable reference points to a scalar variable.

Creating a reference for a scalar variable

To create a scalar variable reference:

my $str = "Hello";
my $str_ref = \$str;

Dereference a scalar variable reference

Use "${}" to dereference the scalar variable reference.

my $str = ${$str_ref};

Simple variable can be dereferenced by simply prefixing them with "$".

my $str = $$str_ref;

Is it worth using a scalar variable reference?

I used a reference when passing a large string to subroutine I think it's faster.

However, in Perl, strings are copied using a technique called copy-on-write, so they are not copied until the strings are actually modified.

So don't worry about large strings, just pass them as subroutine arguments.

Getopt::Long

When programming yourself, you rarely have the opportunity to use a scalar variable reference, but if your library uses them, you need to remember how to use them.

A frequently used module is Getopt::Long.

# Handling command line argument options with GetOptions

# Set default value
my $enable_cache;
my $max_clients = 5;
my $type = 'prefork';

# Optional processing
GetOptions(
  'enable_cache' => \$enable_cache,
  'max_clients = i'=> \$max_clients,
  'type = s'=> \$type
);

Receives non-option arguments
my $conf_file = shift;

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