perldoc -f exec

exec LIST
     exec PROGRAM LIST
             The "exec" function executes a system command and
             never returns-- use "system" instead of "exec" if
             you want it to return.  It fails and returns false
             only if the command does not exist and it is
             executed directly instead of via your system's
             command shell (see below).
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...

my $pid = fork();
if (undefined $pid) {
   die 'Fork failed';
}

if (!$pid) {
   # I am in the child process
   system $MYCOMMAND;
   exit;
}

# I am in the parent process
# continue with other business
...
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