PMC confusion

[Will Coleda]

I can't concat strings to a PerlString, I have to assign the constant
string to another PerlString to do the concat... 

Is this just that a suitable entry in perlstring.pmc needs to be
created?

-----

new P6, PerlString
set      S1, " stuff\n"

# This would fail
# concat   P6, P6, S1

# but putting the string into a pmc works?
new P7, PerlString
set P7, S1
concat P6, P6, P7
print P6
print "\n"
end