.H2 .CVERSION .HIGHLIGHT.OFF
.H2
* .H2 ( value -- )

print hexadecimal, but with per-byte 0-padding 
   0x0     -> 00
   0xf     -> 0f
   0x12    -> 12
   0x123   -> 0123
   0x1234  -> 1234
   0x12345 -> 012345

EXTENSIONS your ordinary primitive