Pad string with characters

Question

I have

$data_dec = 7;
$data_bin = sprintf("%08b",data_dec);

and $data_bin is

00000111

How do I pad with "X" instead of zeros while maintaining 8-bits? Expected data:

XXXXX111

Answer 1

substr( sprintf( "XXXXXXX%b", $n ), -8 )

sprintf( "%8b", $n ) =~ tr/ /X/r