Re^5: Importing constans and variables when "require"ing

used only once doesn't refer to useing, more to using/defining by "mentioning" it. And since you only require XYZ (the module but not the variable XYZ::PI), you are mentioning XYZ::PI only once. The compilation of XYZ.pm, where XYZ::PI is defined, happens only later, during runtime of example.pl , when the require ist actually executed. If you use XYZ instead, Perl sees the declaration of XYZ::PI early enough to avoid the warning.

Comment on Re^5: Importing constans and variables when "require"ing Select or Download Code

Replies are listed 'Best First'.
Re^6: Importing constans and variables when "require"ing by bliako (Abbot) on Feb 24, 2019 at 13:09 UTC
OK thanks. I will confess that I found it weird that the problem is "possible typo" and not complaining because of unknwon variable. Eventually I paid more attention to the so-frequent error message `Global symbol "$x" requires explicit package name (did you forget to declare "my $x"?) at...` I realised that it says "requires explicit package name" whereas I have usually been concentrating on "did you forget to declare?" part. Combined with your message and LanX's `Another effect of strict (vars) is to enforce pre declaration of unqualified variables with my or our.` I get to understand it, hopefully fully. So, evidently, one can get away with declaring variables using my/our completely if it uses fully-qualified variables. So `use strict; $main::x = 42;` will succeed whereas `use strict; $x = 42;` will fail. thanks, bw, bliako	[reply] [d/l] [select]
Re^7: Importing constans and variables when "require"ing by soonix (Chancellor) on Feb 24, 2019 at 18:16 UTC
Yes, but be aware that `$main::x` is a global variable (as in the first error message), which means it can be accessed and modified from anywhere, even outside the corresponding module. So, if once upon a time its value differs from what you expect, you'll have a huge space to search for the culprit. OTOH, if you use scoped (i.e. my) variables, you'll need to search only the correspondig scope. The error message `Global symbol "$x" requires explicit package name` [download] actually means `Do you really want "$x" to be a global symbol?` [download]	[reply] [d/l] [select]