my $string="01100110 01100101 01100101 01101100 01101001 01101110 01100111 00100000 01101100";

#$string=~ s/ (\d+)/pack('B8', $1)/egx; # way 1
$string=~ s/ (\d+)/chr(oct('0b'.$1))/egx;  # way 2