$val will contain the return code from ls.

[system] uses a sub-shell

One of those statments is necessarily false. If a shell is used, $val will contain the return value of the shell, not ls.

So does system use a shell? It depends. "If there is only one scalar argument, the argument is checked for shell metacharacters, and if there are any, the entire argument is passed to the system's command shell for parsing." Otherwise, no.

In this case? no. However, I still wouldn't use ls.

Some examples: 

system('command foobar')      # no shell
system('command "foo bar"')   # shell
system('command', 'foo bar')  # no shell
system('sort < file | uniq')  # shell

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In reply to Re^2: how to store values from system command by ikegami
in thread how to store values from system command by veeruch

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