use strict;
use warnings;

use List::Util qw( max sum );

my @stats = qw( hp mana spells );

my %rates  = ( hp => 12, mana =>  17, spells =>  7 );
my %stats  = ( hp => 60, mana =>  80, spells => 31 );
my %needed = ( hp => 51, mana => 107, spells => 38 );

{
   my $avail = sum @stats{@stats};

   our @parts;
   ('.' x $avail) =~ /
      ^
      (.*) (?(?{  length($1) > $needed{$stats[0]}  })(?!))
      (.*) (?(?{  length($2) > $needed{$stats[1]}  })(?!))
      (.*) (?(?{  length($3) > $needed{$stats[2]}  })(?!))
      \z
      (??{
         push @parts, {
            $stats[0] => length($1),
            $stats[1] => length($2),
            $stats[2] => length($3),
         };
      })
      (?!)
   /x;

   
   my ($result) = sort { $a->[1] <=> $b->[1] }
                  map { my $part = $_;
                        my $time = max
                                   map { ( $needed{$_} - $part->{$_} ) / $rates{$_} }
                                   @stats;
                        [ $_, $time ]
                      }
                  @parts;

   print(join("\t", @stats, 'hours'), "\n");
   printf(join("\t", ("%d")x@stats, "%.2f") . "\n",
      @{$result->[0]}{@stats},
      $result->[1],
   );
}

##</code><code>##

hp      mana    spells  hours
43      95      33      0.71