Simo A's answer is probably right with regards to the issue, but I like to use the following when working with screen opposed to using the -X
flag. Explicitly telling it the command language interpreter.
Why use -c you ask?
If the -c option is present, then commands are read from string. If there are arguments after the string, they are assigned to the positional parameters, starting with $0.
system("screen -dmS $screenname sh -c 'PRETTY MUCH ANYTHING WORKS'");
I figured I'd shared as I run alot of Perl system commands and the above always works for screen commands.