I can think of only two reasons why you "can't do this from the commandline" - one is that the file name you're supplying does NOT exist or does not exist where you think it does -- is, in the directory from which you're executing your code.

The other is that you're on a windows box and need to fix your quotes.

 List.txt
for use with 1011347

server1 ipaddress
server2 ipaddress
server3 ipaddress

D:\> perl -E "undef $/; $text=<>; print $text; $/=\"\n\";" List.txt
[download]

Works for me (the oneliner is as revised for use on the windows box most readily available):

D:\>perl -E "undef $/; $text=<>; print $text; $/=\"\n\";" List.txt

Source file as output by code above

List.txt
for use with 1011347

server1 ipaddress
server2 ipaddress
server3 ipaddress

D:\> perl -E "undef $/; $text=<>; print $text; $/=\"\n\";" List.txt
D:\>
[download]

Or, I suppose, a third possible cause of failure would amount to both the above.   :)