Checking string emptiness

dave93 has asked for the wisdom of the Perl Monks concerning the following question:

In my code I frequently have to write conditions like this:

if (defined $string and $string ne "") {
  .....
}
[download]

What I really want is to check if the string is not entirely empty. I would like to be able to do something like if ($string) but this would exclude "0".

So I hope that there is a shorter and nicer way to do this. For now I have been using a utility strempty subroutine which runs that check but I doubt it's idiomatic.

In my own code I try to have it so that empty strings are simply undef, where applicable, but sometimes it can't be helped and external modules don't follow this rule hence why I have to write these conditions.

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Re: Checking string emptiness by jwkrahn (Abbot) on Apr 04, 2025 at 22:09 UTC
`if ( length $string ) {` [download] I believe that `length` is more efficient than using a string comparison. Naked blocks are fun! -- Randal L. Schwartz, Perl hacker	[reply] [d/l]
Re^2: Checking string emptiness by sleet (Monk) on Apr 04, 2025 at 22:23 UTC
It would need to be `length($string // '')` to avoid uninitialized value warnings.	[reply] [d/l]
Re^3: Checking string emptiness by ikegami (Patriarch) on Apr 05, 2025 at 00:01 UTC
Not since 5.12. `length undef` returns `undef` without warning since then.	[reply] [d/l] [select]
Re: Checking string emptiness by dave93 (Acolyte) on Apr 05, 2025 at 00:01 UTC
Thanks, jwkrahn and sleet. It seems that starting with Perl 5.12 it's valid to call `length` with an undef value. It's a relatively recent change. My only concern with this is that it seems too obtuse, so I wondered if it is really idiomatic. I checked a couple of modules and that seems to be the case. Thanks. I consider this resolved.	[reply] [d/l]
Re: Checking string emptiness by harangzsolt33 (Deacon) on Apr 06, 2025 at 04:13 UTC
There are a few other ways too... `sub isEmpty { return defined $_[0] ? !length($_[0]) : 1; }` [download] `sub isEmpty { defined $_[0] or return 1; return !($_[0] =~ tr\|\|\|c); }` [download] `sub isEmpty { return !(defined $_[0] && $_[0] =~ m/./); }` [download]	[reply] [d/l] [select]
Re^2: Checking string emptiness by GrandFather (Saint) on Apr 06, 2025 at 21:25 UTC
Why try to obfuscate it? Just use `if (length $string) {` as suggested by jwkrahn? Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond	[reply] [d/l]
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