What is the proper way to check if a string is empty in Perl?

Question

I've just been using this code to check if a string is empty:

if ($str == "") {   // ... } 

And also the same with the not equals operator...

if ($str != "") {   // ... } 

This seems to work (I think), but I'm not sure it's the correct way, or if there are any unforeseen drawbacks. Something just doesn't feel right about it.

Answer 1

For string comparisons in Perl, use eq or ne:

if ($str eq "") {   // ... } 

The == and != operators are numeric comparison operators. They will attempt to convert both operands to integers before comparing them.

See the perlop man page for more information.

Answer 2

1. Due to the way that strings are stored in Perl, getting the length of a string is optimized.
   if (length $str) is a good way of checking that a string is non-empty.

2. If you're in a situation where you haven't already guarded against undef, then the catch-all for "non-empty" that won't warn is if (defined $str and length $str).