sub inefficient_qx
{
    my $cmd=shift;
    local *PIPE;
    open PIPE,"$cmd |" or die "Could not open pipe from $cmd";
    #    ^-- intentionally written using an old-style bareword handle for ancient perls
    if (wantarray) {
        my @tmp=<PIPE>;
        close PIPE or die "Close pipe failed: $!";
        return @tmp;
    } else {
        my $tmp=do { local $/=<PIPE> };
        close PIPE or die "Close pipe failed: $!";
        return $tmp;
    }
}

##</code><code>##

> perl -E 'open my $pipe,"-|","pstree --ascii --arguments --long $$ 1>&2" or die $!;'
perl -E open my $pipe,"-|","pstree --ascii --arguments --long $$ 1>&2" or die $!;
  `-sh -c pstree --ascii --arguments --long 22176 1>&2
      `-pstree --ascii --arguments --long 22176
>

##</code><code>##

> perl -E 'open my $pipe,"-|","pstree --ascii --arguments --long $$ 1>&2","dummy" or die $!;'
No such file or directory at -e line 1.
>

##</code><code>##

> perl -E 'system("pstree --ascii --arguments --long $$ 1>&2")==0 or die $!'
perl -E system("pstree --ascii --arguments --long $$ 1>&2")==0 or die $!
  `-sh -c pstree --ascii --arguments --long 20620 1>&2
      `-pstree --ascii --arguments --long 20620


> perl -E 'system("pstree --ascii --arguments --long $$ 1>&2","dummy")'

alex@enterprise pts/0 16:09:53
/home/alex>perl -E 'system("pstree --ascii --arguments --long $$ 1>&2","dummy")==0 or die $!'
No such file or directory at -e line 1.

> perl -E 'exec("pstree --ascii --arguments --long $$ 1>&2") or die $!'
sh -c pstree --ascii --arguments --long 20657 1>&2
  `-pstree --ascii --arguments --long 20657

> perl -E 'exec("pstree --ascii --arguments --long $$ 1>&2","dummy") or die $!'
No such file or directory at -e line 1.

>

##</code><code>##

> perl -E '@list=("pstree --ascii --arguments --long $$ 1>&2"); system { $list[0] } @list and die $!'
No such file or directory at -e line 1.

> perl -E '@list=("pstree --ascii --arguments --long $$ 1>&2"); exec { $list[0] } @list or die $!'
No such file or directory at -e line 1.

>