=begin maintainer_notes

Since I *am* a Perl 5 programmer coming to Perl 6 for the first time, it
seems appropriate to make notes on what I needed to get used to in Perl
6.  I'm going to start out more or less making a running list of items,
and then I guess they can be organised more neatly later on.  -- KR

=end maintainer_notes

=head1 NAME

Perl6::Perl5::Differences -- differences between Perl 5 and Perl 6

=head1 DESCRIPTION

This document is intended to be used by Perl 5 programmers who are new
to Perl 6 and just want a quick overview of the main differences.  More
detail on everything can be found in the language reference.

The ordering of this document is more or less in order from basic stuff
to complex stuff.  To put it another way, it's been written in the order
that the topics came up while the author was learning Perl 6.

=head2 say()

This is a version of print() that auto-appends a newline:

    Was:    print "Hello, world!\n";
    Now:    say   "Hello, world!";

Since you want to do that so often anyway, it seemed like a handy thing
to make part of the language.

=head2 Sigils

Where you used to say:

    my @fruits = ("apple", "pear", "banana");
    print $fruit[0], "\n";

You would now say:

    my @fruits = ("apple", "pear", "banana");
    say @fruit[0];

Or even use the C<< <> >> operator, which replaces C<qw()>:

    my @fruits = <apple pear banana>;

Note that the sigil for fetching a single element has changed from C<$>
to C<@>; perhaps a better way to think of it is that the sigil of a
variable is now a part of its name, so it never changes in subscripting.

The same applies to hashes:

    say "There are %days{'February'} days in February";

Again, there is a shorter form:

    say "There are %days<February> days in February";

=head2 New ways of referring to array and hash elements

Number of elements in an array: 

    Was:    $#array+1 or scalar(@array)
    Now:    @array.elems

Index of last element in an array:

    Was:    $#array
    Now:    @array.end

Therefore, last element in an array:

    Was:    $array[$#array]
    Now:    @array[@array.end]
            @array[-1]              # also works

Hash elements no longer auto-quote:

    Was:    $days{February}
    Now:    %days{'February'}
    Or:     %days{"February"}
    Or:     %days<February>
    Or:     %days<<February>>

The curly-bracket forms still work, but curly-brackets are more
distinctly block-related now, so in fact what you've got there is a
block that returns the value "February".  The C<<>> and C<<<>>> forms
are in fact just quoting mechanisms (see below).

=head2 q(), qq(), etc have changed

    Was:    q(foo)
    Now:    <foo>

    Was:    qq(foo)
    Now:    <<foo>>

=head2 Method invocation changes from -> to .

    Was:    $object->method
    Now:    $object.method

=head2 Built-in functions are now methods

Most (all?) built-in functions are now methods of built-in classes such
as String, Array, etc.

    Was:    my $len = length($string);
    Now:    my $len = $string.chars;

    Was:    print sort(@array);
    Now:    print @array.sort;
            @array.sort.print;

You can still say C<sort(@array)> if you prefer the non-OO idiom.

=head2 You don't need parens on control structure conditions

    Was:    if ($a < $b) { ... }
    Now:    if  $a < $b  { ... }

Likewise for C<while>, C<for>, etc.

=head2 foreach becomes for

    Was:    foreach (@whatever) { ... }
    Now:    for @whatever       { ... }

Also, the way of assigning to something other than C<$_> has changed:

    Was:    foreach my $x (@whatever) { ... }
    Now:    for @whatever -> $x       { ... }

This can be extended to take more than one element at a time:

    Was:    while (my($age, $sex, $location) = splice @whatever, 0, 3) { ... }
    Now:    for @whatever -> $age, $sex, $location { ... }

(Only the C<for> version does not destroy the array.)

=head2 for becomes loop

    Was:    for  ($i=0; $i<10; $i++) { ... }
    Now:    loop ($i=0; $i<10; $i++) { ... }

=head1 AUTHOR

Kirrily "Skud" Robert, <skud@cpan.org>