Hi McA Thanks, you have solved one of the two problems - getting "say" to work. The other problem - not being able to execute the script with "." still exists:

~/perl
J-PC:J >cat hello.pl
#!/usr/bin/perl

use warnings;
use v5.10.0;
say "hello";
~/perl
J-PC:J >perl hello.pl
hello
~/perl
[download]

But I cannot execute the script with "." :

J-PC:J >. hello.pl
-bash: use: command not found
-bash: use: command not found
-bash: say: command not found
~/perl
J-PC:J >
[download]

I have added /usr/bin/perl to my $PATH variable, although I don't think that should be necessary because the script has /usr/bin/perl at the top of it. I have also put +x perms on the script.
Update:
=======
I should say that I just tried running with "./hello.pl" rather than ". hello.pl" and it worked. IIRC using ". " i.e. dot space runs a command in a separate process (or summat...it's been a while)...but as far as I remember there's no reason why a command might run using "./<command>" rather than ".space<command>"