use strict;
use warnings;
use Data::Dump qw(dump);

$_ = $0;
my %h;

sub f { print('->f()') . '.0'; }

$h{  f  } =  '  F';
$h{ +f  } =  ' +F';
$h{+ f  } =  '+ F';
$h{ -f  } =  ' -F';
$h{- f  } =  '- F';
$h{  f()} =  ' ()';
$h{ -f()} =  '-()';
$h{- f()} =  '-()';
$h{ +f()} =  '+()';
print "\n",dump(\%h),"\n";


##</code><code>##

->f()->f()->f()->f()->f()
{ "-1" => "-()", "-f" => "- F", "1" => "-()", "1.0" => "+()", "f" => "  F" }

##</code><code>##

use strict;
use warnings;
use Data::Dump qw(dump);

$_ = $0;
sub f { print('->f()') . '.0'; }

my %h = (
     f    => '  F',
    +f    => ' +F',
   + f    => '+ F',
    -f    => ' -F',
   - f    => '- F',
     f()  => ' ()',
    -f()  => '-()',
   - f()  => '-()',
    +f()  => '+()',
);
print "\n",dump(\%h),"\n";


##</code><code>##

->f()->f()->f()
{ "-1" => "-()", "-f" => "- F", "1" => "-()", "1.0" => "+()", "f" => "+ F" }