Be less restrictive and allow also `perl util/perlpath.pl /path/to/bin/perl'

in addition to `perl util/perlpath.pl /path/to/bin', because this way one can
also use an interpreter named `perl5' (which is usually the name of Perl 5.xxx
on platforms where an Perl 4.x is still installed as `perl').

Submitted by: Matthias Loepfe <Matthias.Loepfe@adnovum.ch>
Reviewed by: Ralf S. Engelschall