$ perl5420 -v
This is perl 5, version 42, subversion 0 (v5.42.0) built for x86_64-linux
$ perl5420 ~/tmp/p
doing arg
match
match
$ perl5420t -v
This is perl 5, version 42, subversion 0 (v5.42.0) built for x86_64-linux-thread-multi
$ perl5420t ~/tmp/p
doing arg
match
doing arg
match
$