Musing about the lack of enumerations in Perl and what best to use as "symbols", I benchmarked the speed of comparing numbers, strings, and refs (code below). As expected, numbers are faster. But most unexpectedly, refs are rather slow! I would have thought that it would be about the same as for a number, since it just compares addresses. Anybody know what the story is on this?

use strict;
use warnings;
use Benchmark 'cmpthese';

my ($sym1, $sym2, $sym3, $sym4);

sub strings
 {
 if ($_[0] eq "yes")  { return 1; }
 elsif ($_[0] eq "no")  { return 0; }
 elsif ($_[0] eq "maybe")  { return 2; }
 elsif ($_[0] eq "foo")  { return 3; }
 return undef;
 }

sub numbers
 {
 if ($_[0] == 42)  { return 1; }
 elsif ($_[0] == 33)  { return 0; }
 elsif ($_[0] == 99)  { return 2; }
 elsif ($_[0] == 69)  { return 3; }
 return undef;
 }

sub refs
 {
 if ($_[0] == \$sym1)  { return 1; }
 elsif ($_[0] == \$sym2)  { return 0; }
 elsif ($_[0] == \$sym3)  { return 2; }
 elsif ($_[0] == \$sym4)  { return 3; }
 return undef;
 }

cmpthese (0,
 { 'strings 2' => sub { strings ("no") },
 'strings 4' => sub { strings ("notfound") },
 'numbers 2' => sub { numbers (33) },
 'numbers 4' => sub { numbers (99999) },
 'refs 2' => sub { refs (\$sym2); },
 'refs 4' => sub { refs (\&refs); }
 });

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—John

In reply to speed of comparisons of things by John M. Dlugosz

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