You are both right. Under HP-UX it depends on the command used to start the script. If you start it with the full path, you will get the full path. If you start it with a relative value, you will get a relative value. That also goes for the shebang line.

$ /usr/contrib/bin/perl -e 'print $^X, "\n"'
/usr/contrib/bin/perl
$ perl -e 'print $^X, "\n"'
perl
$ uname -a
HP-UX noway B.11.00 A 9000/800 xxxxxxxx two-user license
$ perl -e 'print $^O, "\n"'
hpux
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