Question

I have a situation where I expect variables to be passed to me as strings or numbers.

i.e.

sub foo {
    # These can be either strings or numbers
    my ($bar, $var, $star) = @_;

    # I need to check to see if $bar is the number 0 (zero)
    if ($bar == 0) {
        # Do super magic with it
    }
}

Unfortunately Perl tries to do the super magic on $bar when it contains a string.

How can I tell Perl to do super magic on $bar if and only if it is the number 0 (zero)?

I understand Perl fundamentally interprets based on context, which is the underlying problem here. A possible solution to this problem is to use regex, which is fine, but I wanted to know if there was another more “straight-forward” solution.

Thanks in advance.

Answer 1

I’d personally go with what @Disco3’s comment said.

if ($bar eq 0) { ... }

This works for $bar = 0, $bar = 'foo' and $bar = 123 giving the expected result.

Here’s a fun fact, though:

use Benchmark qw(cmpthese);
my $bar = '0';

cmpthese(-1, {
  'quoted'    => sub { $bar eq '0'    },
  'unquoted'  => sub { $bar eq 0      },
  'regex'     => sub { $bar =~ m/^0$/ },
});

Benchmarking these three solutions tells us that the unquoted 0 is the fastest way to do it.

               Rate    regex   quoted unquoted
regex     4504851/s       --     -70%     -76%
quoted   15199885/s     237%       --     -19%
unquoted 18828298/s     318%      24%       --