Not a s/printf specifier but, for pre-5.22, there's Data::Float's float_hex() function: 
C:\>perl -MData::Float="float_hex" -le "print float_hex(1 / 9);"
+0x1.c71c71c71c71cp-4

[download]
Cheers,
Rob

In reply to Re: Hex floating point format specifier? by syphilis
in thread Hex floating point format specifier? by BrowserUk

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