5.26 in entirely correct: https://metacpan.org/release/XSAWYERX/perl-5.26.0/changes

For security reasons, the current directory (".") is no longer included by default at the end of the module search path (@INC). This may have widespread implications for the building, testing and installing of modules, and for the execution of scripts. See the section "Removal of the current directory (".") from @INC" for the full details.