Under AIX when I'm running as root, I can't seem to set $< (aka $UID) properly...

# perl -e '$< = 81'
setruid() not implemented at -e line 1.
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I can understand this, since this function doesn't exist on AIX. Is there a workaround here to get perl to execute the C function setuid() instead? I'd really like to do something like this...

$pid = fork;
die unless defined $pid;
unless ($pid) {
    $< = $> = $bobs_uid;
    exec "foo";
}
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... so that the child runs unpriviledged.

I can't just set $> ($EUID) since the child can just set it back to zero. I can't use POSIX::setuid() since that give the same error. I suppose I could do something outside of perl like use a C wrapper that calls setuid() or something grotesque like...

system("su bob -c foo &");  #syntax?
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... but I'd really like to do this in perl.

Thanks