As i do not know ClearCase and how that accept works, i can only guess. Seeing how it is an error message, it might be written to STDERR instead of STDOUT and backticks only capture STDOUT of the command executed. In that case, redirecting the commands STDERR to STDOUT would work. Try
$acceptA = `accept $Component 2>&1`
and see if that works in capturing the output in case of error as well.