TIMTOWTDI

Just stick your internal functions in their own package and use the package hash :)

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11163188
use warnings;
use List::AllUtils qw( sample );

(sample 1, values %INTERNALFUNCTIONS::)->() for 1 .. 5;

package INTERNALFUNCTIONS;

sub TestSub1 {
    print "TestSub1\n";
}

sub TestSub2 {
    print "TestSub2\n";
}
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Outputs:

TestSub1
TestSub2
TestSub2
TestSub1
TestSub1
[download]

Still strict, no fancy manipulations required, and you can dynamically add more functions :)
Perl sure has some interesting tricks up its sleeve.