include/eval perl file into unique namespace defined at runtime - perl

Question

I'm writing a tool that must import a number of other perl config files. The files are not wrapped w/packages and may have similar or conflicting variables/functions. I don't have the ability to change the format of these files, so I must work around what they are. What I was thinking to do was import each into a unique name space, but I've not found a way to do that using do, require, or use. If I don't use dynamic names, just a hardcoded name, I can do it.
Want something like this:
sub sourceTheFile {
my ($namespace, $file) = #_;
package $namespace;
do $file;
1;
return;
}
That doesn't work because the package command requires a constant for the name. So then I try something like this:
sub sourceTheFile {
my ($namespace, $file) = #_;
eval "package $namespace;do $file;1;"
return;
}
But the contents of the file read by do are placed in the main:: scope not the one I want. The target scope is created, just not populated by the
do. (I tried require, and just a straight cat $file inside the eval as well.)
I'm using Devel::Symdump to verify that the namespaces are built correctly or not.
example input file:
my $xyz = "some var";
%all_have_this = ( common=>"stuff" );
ADDITIONAL CHALLENGE
Using the answer that does the temp file build and do call, I can make this work dynamically as I require. BUT, big but, how do I now reference the data inside this new namespace? Perl doesn't seem to have the lose ability to build a variable name from a string and use that as the variable.

Answer 1

I am not sure why the eval did not work. Maybe a bug? Here is a workaround using a temp file. This works for me:
use strict;
use warnings;
use Devel::Symdump;
use File::Temp;
my $file = './test.pl';
my $namespace = 'TEST';
{
my $fh = File::Temp->new();
print $fh "package $namespace;\n";
print $fh "do '$file';\n";
print $fh "1;\n";
close $fh;
do $fh->filename;
}

Answer 2

Perl's use and require facilities make use of any hooks you might have installed in #INC. You can simply install a hook which looks in a specific location to load modules with a prefix you choose:
package MyIncHook;
use strict;
use warnings;
use autouse Carp => qw( croak );
use File::Spec::Functions qw( catfile );
sub import {
my ($class, $prefix, $location) = #_;
unshift #INC, _loader_for($prefix, $location);
return;
}
sub _loader_for {
my $prefix = shift;
my $location = shift;
$prefix =~ s{::}{/}g;
return sub {
my $self = shift;
my $wanted = shift;
return unless $wanted =~ /^\Q$prefix/;
my $path = catfile($location, $wanted);
my ($is_done);
open my $fh, '<', $path
or croak "Failed to open '$path' for reading: $!";
my $loader = sub {
if ($is_done) {
close $fh
or croak "Failed to close '$path': $!";
return 0;
}
if (defined (my $line = <$fh>)) {
$_ = $line;
return 1;
}
else {
$_ = "1\n";
$is_done = 1;
return 1;
}
};
(my $package = $wanted) =~ s{/}{::}g;
$package =~ s/[.]pm\z//;
my #ret = (\"package $package;", $loader);
return #ret;
}
}
__PACKAGE__;
__END__
Obviously, modify the construction of $path according to your requirements.
You can use it like this:
#!/usr/bin/env perl
use strict;
use warnings;
use MyIncHook ('My::Namespace', "$ENV{TEMP}/1");
use My::Namespace::Rand;
print $My::Namespace::Rand::settings{WARNING_LEVEL}, "\n";
where $ENV{TEMP}/1/My/Namespace/Rand.pm contains:
%settings = (
WARNING_LEVEL => 'critical',
);
Output:
C:\Temp> perl t.pl
critical
You can, obviously, define your own mapping from made up module names to file names.