sub foo { print "hello world" };

# more or less equivalent to:
BEGIN {
  *foo = sub { print "hello world" };
}

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;

my $i = 1;
sub counter_i { $i++ }

sub counter_gen {
    my $j = shift;
    return sub { $j++ }
}

my @counters = ( \&counter_i, counter_gen(5), counter_gen(10) );

for ( 1 .. 10 ) {
    for my $c ( @counters ) {
        print $c->(), " ";
    }
    print "\n";
}

##</code><code>##

1 5 10
2 6 11
3 7 12
4 8 13
5 9 14
6 10 15
7 11 16
8 12 17
9 13 18
10 14 19