require v5.20;
feature->unimport::out_of( $caller, ':all' );  # `use v5.10;`+
feature->import::into( $caller, ':5.20' );     # `use v5.10;`+
strict->import::into( $caller );               # `use v5.12;`+
#warnings->import::into( $caller );            # `use v5.35;`+