perldoc -f system or the 'backtick' operator is the simplest. Returns a string containing the output.

If you want to send something to the command's input stream or read from its output stream a line at a time, use the piped open:

open FIL,'cmd arg arg|' or die "Failed to fork, $!";
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If you need to do both reading and writing, use open3, or for a more friendly API, you might like to try IPC::Open3