Notice that you don't HAVE to use namespaces with require or use. All of that stuff is just conventions (though the import that can be implicit in use will be to what the package name seems to be). And it's usually nicer to use "use" than "require" or "do" even for "include", since you will see any errors before runtime of the main program gets there, subs in there are already known to the compiler when it's compiling your main code, and there is some implicit checking that the "included" code didn't crash.

So it's perfectly ok to e.g. have a Foo.pm file containing:

# Warnings, strict and our aren't needed if you don't 
# want to bother. I Just like to have them
use strict;
use warnings;
our $c = 5;
sub foo {
    print $c;
}

# Next line is the only thing that's different from
# what you'd have if you were going to use "do"
# A filed being required/used should return something true
1;
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And then use that as:

use Foo();
use strict;
# you couldn't call foo without () under use strict 
# if you had used "require" or "do"
foo;
our $c;
print $c;
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Notice the () in use Foo(). It avoids a call to import, though supposedly if you use this you won't have a Foo package and there will be no import there, so you could leave them out too.

Having said that, it's still often a good idea to make commonly used code into a real module. You can use the Exporter if you want subs and variables in there available unqualified in your main code. It's only a few trivial lines more:

package Foo;                 # This line is new
use strict;
use warnings;
use base qw(Exporter);       # This line is new
our @EXPORT_OK =qw($c foo);  # This line is new, stuff the caller MAY 
+import to use it unqualified
our $c = 5;
sub foo {
    print $c;
}

1;
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And on use you have to say which of the exported things you'd like to use:

# Next line is different, explicitely say we want to use foo unqualifi
+ed (without Foo::)
use Foo qw(foo);            
use strict;
foo;
# We could also have listed $c in the import list and then use plain $
+c
# But let's instead show you can still access it by qualifying 
print $Foo::c;
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