Re^3: Conditional initialization of my-variables

> or to add a default value

> $input = 1 unless $input;

Careful! Many things are false in Perl, like 0 or ""

You probably meant

$input = 1 unless defined $input;

Anyway, both are IMHO better written as

$input ||= 1;  # default if false
               # or 
$input //= 1;  # default if undefined
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Cheers Rolf
_{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :)

Wikisyntax for the Monastery}

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Re^4: Conditional initialization of my-variables by Bod (Parson) on Apr 08, 2023 at 17:55 UTC
Careful! Many things are false in Perl, like 0 or "" Oh yes - care is needed. But very often that's exactly what I want. A common use case is query strings from HTML forms with checkboxes. The query string will have the key with no value. So if that's decoded into a Perl hash, the hash will be `defined` and the key `exists` but I want it to return false as it is an empty string.	[reply] [d/l] [select]
Re^5: Conditional initialization of my-variables by LanX (Saint) on Apr 08, 2023 at 18:24 UTC
When dealing with empty strings, I'd rather check `length` Edit `DB<13> p "false" unless "0" false DB<14> p "false" unless 0 false DB<15> p "false" unless length "0" DB<16> p "false" unless length undef false DB<17> use warnings; length undef DB<18> p "false" unless length "" false DB<19>` [download] Cheers Rolf _{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l]
Re^6: Conditional initialization of my-variables by kcott (Archbishop) on Apr 08, 2023 at 19:49 UTC
"When dealing with empty strings, I'd rather check `length`" I concur; however, for anyone using a version prior to `v5.14.0`, a few things to note: Prior to `v5.12.0`, the operand needed to be defined to avoid a "Use of uninitialized value" warning. [length() doco for v5.10.1] `v5.12.0` allowed the operand to be `undef` (see "perl5120delta: Other potentially incompatible changes"). However, there was a bug (see next point). [length() doco for v5.12.0] `v5.14.0` fixed that bug (from last point): "perl5140delta: Syntax/Parsing Bugs". — Ken	[reply] [d/l] [select]

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