|Do you know where your variables are?|
Well ... having created the perl5.21.3->perl symlink from the terminal (as opposed to over the ssh network connection), I left that symlink in place.
That didn't make any difference to my existing ssh connection immediately - I still had 'which perl' reporting blead, but 'perl' loading the system perl. However, after a few path changes to run different perls, all suddenly started working perfectly when I came back to using blead over the ssh connection. Out of the blue, 'which perl' reported blead (as before) but 'perl' now loaded blead instead of the system perl.
Buggered if I know what the problem was, or what the solution was, but I'll try to re-create the problem next time I build blead.
If I can find something definitive, I'll update this thread with the info.