Definitely a better idea to fix the old code, but ... would something like this DWYW?

#!/usr/bin/perl -w

use strict;
BEGIN {
  local %INC = %INC;
  require PackageA;
  import PackageA if UNIVERSAL::can('PackageA', 'import');
}
BEGIN {
  local %INC = %INC;
  require PackageB;
  import PackageB if UNIVERSAL::can('PackageB', 'import');
}
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