in reply to Variables in a single file

If you use use or require, Perl makes sure that the module (or simply a codeblock of variable declarations) is loaded only once.  Note, however, that the loaded file has its own implicit lexical scope — which matters for variables declared with my or our ...

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Re^2: Variables in a single file
by LanX (Saint) on Sep 16, 2009 at 13:41 UTC
    Unfortunately accessing an undeclared variable which was required from another file can lead to "undefined variable"-warnings.

    Importing with use might be more complicated but it works with warnings enabled.

    @OP: You may wanna have a look at Exporter

    Cheers Rolf

    UPDATE: added "undeclared"

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      ...can lead to "undefined variable"-warnings

      Could you provide an example?  I think you're fine as long as you make sure the code has loaded/compiled before you access the variables (using use or require within a BEGIN block): 

      ---- X.pm ----
$::foo = "foo";
$::bar = "bar";
--------------

#!/usr/bin/perl
use strict;
use warnings;
use X;   # or BEGIN { require X; }

print "$::foo\n";   # no warnings

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        sorry, my memory was wrong one gets a

        Name "main::x" used only once: possible typo at ... warning.

        But putting the require into a begin block really helps. 8)

        > cat mod.pm tren prog.pl tren; perl prog.pl
$x="X";
 
1;
------------------------
use strict;
use warnings;
 
#our $x;
#BEGIN { 
  require mod; 
#}
 
 
print $::x;
------------------------
Name "main::x" used only once: possible typo at prog.pl line 10.
X

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        Cheers Rolf

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