I suppose it's also worth mentioning that my and our have two other friends: local and state.

local sets a new, temporary value for a package variable, which expires at the end of the current scope, with the variable's original value being restored.

In this example, bar() sets $::hello temporarily to "Goodbye" and this new value is visible to foo(), but after bar() has finished running, the original value of "Hello" is restored again.

use v5.14;

sub foo
{
    say $::hello;
}

sub bar
{
    local $::hello = "Goodbye";
    foo();
}

$::hello = "Hello";
bar();
say $::hello;
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And state can be used to create a variable which keeps its state, not being re-initialised.

use v5.14;

sub counter {
    state $count = 1;
    say $count++;
}

counter();
counter();
counter();
counter();
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