sub outer
{
  my $a = 123;

  sub inner
  {
    print $a, "n";
  }

  # At this point, $a is 123, so this call should always print 123, right?
  inner();

  $a = 456;
}

outer(); # prints 123
outer(); # prints 456! Surprise!

sub outer
{
  my $a = 123;

  my $inner = sub
  {
    print $a, "n";
  };

  # At this point, $a is 123, and since the anonymous subrotine
  # whose reference is stored in $inner closes over $a in the
  # "expected" way...
  $inner->();

  $a = 456;
}

# ...we see the "expected" results
outer(); # prints 123
outer(); # prints 123

sub find_files
{
  my @files;

  my $wanted = sub
  {
    if($something)
    {
      push @files, $File::Find::name;
    }
  };

  # The find() function called here is imported from File::Find
  find({ wanted => $wanted }, $directory);

  return @files;
}

#!/usr/bin/perl

use strict;
use warnings;

sub generate_multiplier {
    my ($coef) = @_;

    return sub {
        my ($val) = @_;
        $coef * $val;
    }
}

my $doubler = generate_multiplier(2);
my $tripler = generate_multiplier(3);

for my $i ( 1 .. 10 ) {
    printf "%4d%4d%4dn", $i, $doubler->($i), $tripler->($i);
}

__END__

C:Temp> v
    1   2   3
    2   4   6
    3   6   9
    4   8  12
    5  10  15
    6  12  18
    7  14  21
    8  16  24
    9  18  27
   10  20  30

sub Foo { stuff() }

BEGIN { *Foo = sub { stuff() } }  # essentially equivalent

use 5.010;
use strict;
use warnings;

sub make_iterator {
  my @list = @_;
  return sub { shift @list }; # new sub that 'remembers' @list
}

my $iter1 = make_iterator( 0 .. 10 );
my $iter2 = make_iterator( 'a' .. 'z' );

say $iter1->();  # '0'
say $iter1->();  # '1'
say $iter2->();  # 'a'

my @sorted_array = sort { $a <=> $b } @array;

use strict;
use warnings;

sub xx {
  my $zz=1;

   sub yy {
      print $zz;
   }
}


perl tmp.pl
Variable "$zz" will not stay shared at tmp.pl line 8.

# jump table to subroutines / variables
my %jump = (
  id     => 'id',
  xid    => 'xid',
  hex_id => 'xid',

  h      => &h,
  mac    => &mac,
  sed    => &sed,
  make   => &make,
  nsis   => &nsis,

  perl   => &perl,
  dump   => &perl,
  yaml   => &yaml,
  yml    => &yaml,
  json   => &json,
  js     => &json,

  help   => &help,
  usage  => sub{
    require Pod::Usage;

    Pod::Usage::pod2usage(
      "run perldoc $0 or pod2text $0 for more information"
    );
  }
);