Your friend is absolutely right!  Calling perl a programming language is like calling emacs a word processor.  Perl is a collection of tools for getting things done on a computer.  It uses language to refer to said tools.  In that sense it is a language with which to program computers which I suppose is where the confusion creeps in.  But to call it a computer language as if it were like one of these algebraically defined Computer Languages is a canard which should not be tolerated.