that doesn't work

Oh, but it does "work"; and has done since perl 4 days. Here's proof:

fred.pm:

#package fred;

sub X123{ return 'x123'; }

sub Y456 { return 'Y456'; }

$localScalar = 'from fred';
@localArray = qw[ also from fred ];
%localHash = qw[ and this comes from fred as well ! ];

print 'fred.pm loaded';
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And junk33.pl that does it:

#! perl -slw

do './fred.pm' or die "$@ / $!";

print $localScalar;
print @localArray;
print %localHash;

print X123();
print Y456();
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And the output from a run:

C:\test>junk33
fred.pm loaded
from fred
alsofromfred
well!comesfromandthisfredas
x123
Y456
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See subs and variables 'exported' into the calling code.

Of course, if you enable warnings, you do get a few:

C:\test>junk33
Name "main::localArray" used only once: possible typo at C:\test\junk3
+3.pl line 6.
Name "main::localHash" used only once: possible typo at C:\test\junk33
+.pl line 7.
Name "main::localScalar" used only once: possible typo at C:\test\junk
+33.pl line 5.
fred.pm loaded
from fred
alsofromfred
well!comesfromandthisfredas
x123
Y456
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And if you enable strict, things start to fall apart:

C:\test>junk33
Global symbol "$localScalar" requires explicit package name at C:\test
+\junk33.pl line 6.
Global symbol "@localArray" requires explicit package name at C:\test\
+junk33.pl line 7.
Global symbol "%localHash" requires explicit package name at C:\test\j
+unk33.pl line 8.
Execution of C:\test\junk33.pl aborted due to compilation errors.
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And that is my point. do 'file' is "is almost forgotten, little used syntax," for a reason; Perl 5 vastly improved upon the mechanisms available in Perl4, by introducing packages & namespaces & lexical variables, and the tools (require & use) to make use of them.

And in order to achieve what you are asking for in the OP, is to return to Perl4 -- which Perl will allow you to do -- but to achieve it you need to throw away namespaces and packages and lexical variables and strict & warnings. If you're prepared to do that, perl makes it simple. If you are not; then you might reconsider the reasons why you want to do it.

I could have told you: thou shalt not; but it's better that you understand the reasons why it probably better that you don't; that you understand the trade offs; and what you have to give up in order to avoid re-structuring the code that you are so adamant that you cannot do.

In other words; what you are asking for is doable; but given the trade-offs, you'll probably decide that you don't actually want to do it any more. But it is your decision to make.