为什么 -le,-el？

为什么 -le,-el？
[code]
[biozy@node11 bin]$ perl -le '$a=qq/asbd/;$b=reverse($a);print $b'
dbsa
[/code]
而下面的就不可以了？难道-le,-el还有顺序吗？
[code]
[biozy@node11 bin]$ perl -el '$a=qq/asbd/;$b=reverse($a);print $b'
[biozy@node11 bin]$
[/code]

谢过，知道了---e comma.
谢过，知道了
-e commandline
may be used to enter one line of program. If -e is given, Perl
will not look for a filename in the argument list. Multiple -e
commands may be given to build up a multi-line script. Make sure
to use semicolons where you would in a normal program.