Is there a string in Perl that is equal to all other strings under eq?

Question

I am running a string equality check like this:

if($myString eq "ExampleString")

Is there a value that myString could have which would cause execution to enter the if structure no matter what the string literal is?

Answer 1

Yes, with objects and overloaded operators:

package AlwaysTrue {
  use overload 'eq' => sub { 1 },
               '""' => sub { ${+shift} };
  sub new {
    my ($class, $val) = @_;
    bless \$val => $class;
  }
}

my $foo = AlwaysTrue->new("foo");

say "foo is =$foo=";
say "foo eq bar" if $foo eq "bar";

Output:

foo is =foo=
foo eq bar

However, "$foo" eq "bar" is false, as this compares the underlying string.

Answer 2

If you mean "any string other than undef", then simply check

if (defined $myString)

If you mean "any string other than undef or empty string", then simply check

if ($myString) # Has a slight bug - will NOT enter if the number 0 passed
#or
if ($myString || $myString == 0)  # Avoids the above bug

If you mean ANY ANY string, you don't need an if.... but if you want one anyway:

if (1)

If you mean "any string that isn't looking like a number" (e.g. distinguish "11" from "11a"):

use Scalar::Util qw(looks_like_number);
if (Scalar::Util::looks_like_number($myString))