8.7.whatever because ("8" | "7") eq "?" and "?" == 0 so ("8" | "7") == 0.

In fact, here's the key.

$\ = "\n";

print chr() . ", " . unpack( "B*", chr ) for ord( "0" ) .. ord( "9" );
print;
print chr() . ", " . unpack( "B*", chr ) for ord( "2" | "8" ) .. ord( 
+"7" | "8" );
__DATA__
0, 00110000
1, 00110001
2, 00110010
3, 00110011
4, 00110100
5, 00110101
6, 00110110
7, 00110111
8, 00111000
9, 00111001

:, 00111010
;, 00111011
<, 00111100
=, 00111101
>, 00111110
?, 00111111
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