use File::Spec;

sub find_in_path {
    my $prog = shift;
    my $fmm;
    for my $d (File::Spec->path()) {
        $fnm = File::Spec->catfile($d,$prog);
        last if -x fnm;
        $fnm = undef;
    }
    return $fnm;
}

my $excel = find_in_path('excel.exe');