$ perl -le '
> %h = map ( $_, 2 * $_ ), 1 .. 3;
> print qq{$_ - $h{$_}} for sort {$a <=> $b} keys %h;'
0 - 
$

##</code><code>##

$ perl -le '
%h = map @$_, map [ $_, 2 * $_ ], 1 .. 3;
print qq{$_ - $h{$_}} for sort {$a <=> $b} keys %h;'
1 - 2
2 - 4
3 - 6
$

##</code><code>##

$ perl -le '
%h = map sub { return ( $_, 2 * $_ ) }->( $_ ), 1 .. 3;
print qq{$_ - $h{$_}} for sort {$a <=> $b} keys %h;'
1 - 2
2 - 4
3 - 6
$

##</code><code>##

$ perl -le '
%h = map { $_, 2 * $_ } 1 .. 3;
print qq{$_ - $h{$_}} for sort {$a <=> $b} keys %h;'
1 - 2
2 - 4
3 - 6
$

##</code><code>##

$ perl -le '
%h = map ( ( $_, 2 * $_ ), 1 .. 3 );
print qq{$_ - $h{$_}} for sort {$a <=> $b} keys %h;'
1 - 2
2 - 4
3 - 6
$

##</code><code>##

$ perl -le '
> %h = map do { ( $_, 2 * $_ ) }, 1 .. 3;
> print qq{$_ - $h{$_}} for sort {$a <=> $b} keys %h;'
1 - 2
2 - 4
3 - 6
$