As stated update: following is accurate as to output, but NOT as to the process. See jwkrahn's (above) and BrowserUK's (below).
on w2k w/ perl, v5.8.8 built for MSWin32-x86-multi-thread (with 33 registered patches) ... Binary build 819 [267479] provided by ActiveState....

C:\Documents and Settings\ww>perl -e "my $dir=system(dir);print $dir
 Volume in drive C has no label.
 Volume Serial Number is 704A-B003

 Directory of C:\Documents and Settings\ww

01/03/2010  06:29a      <DIR>          .
01/03/2010  06:29a      <DIR>          ..
07/16/2007  06:03a                 107  .bps
12/29/2009  07:46p      <DIR>          .gimp-2.6
08/13/2007  11:40a      <DIR>          .housecall6.6
12/23/2009  10:55a               1,480 .recently-used.xbel
11/14/2009  10:44a      <DIR>          .thumbnails

... #more files and dirs


02/16/2008  11:37a      <DIR>          Start Menu
06/29/2007  10:15p                 145 t.net-1.bps
06/29/2007  10:13p                 145 t.net.bps
              20 File(s)      8,026,977 bytes
              10 Dir(s)   6,957,117,440 bytes free
0
C:\Documents and Settings\ww>
[download]

The only bit of that output that came from the perl print statement was the final 0. If you doubt it, omit the print and re-run it.