yeah not trivial, you need to temporarily redefine AUTOLOAD in the callers package:

use strict;
use warnings;
use feature 'say';


package DSL;

our $AUTOLOAD;

sub within (&) {
  my $c_block=shift;
  
  #say
    my $call_pkg=((caller)[0]);

  # use B::Deparse;
  # say B::Deparse->new()->coderef2text($c_block);

  no warnings qw/redefine once/;
  no strict qw/refs/;
    
  local *{ ${call_pkg} . "::AUTOLOAD" } = 
     sub { say "Autoload called as $AUTOLOAD(@_)" };

  $c_block->();
  
}



package TEST;

DSL::within {
  &BLA;
  BLUB(2,3,4);
};

#  with import
sub within (&);
*within=\&DSL::within;

within {
  &BLAi;
  BLUBi(2,3,4);
};



BLX();

  
__END__
Autoload called as TEST::BLA()
Autoload called as TEST::BLUB(2 3 4)
Autoload called as TEST::BLAi()
Autoload called as TEST::BLUBi(2 3 4)
Undefined subroutine &TEST::BLX called at /home/lanx/perl/exp/DSL.pl l
+ine 48.
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