in reply to integer container for float

You can check that a native int will hold a native double:

use Config;

die "Int/double size mismatch" unless $Config{ ivsize } == $Config{ nv
+size };

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And if you get passed that test, then the following should always work:

$packedDoubleAsInt = unpack 'Q', pack 'd', 3.14159265358979;;

print $packedDoubleAsInt;;
4614256656552045841

$unpacked = unpack 'd', pack 'Q', $packedDoubleAsInt;;

print $unpacked;;
3.14159265358979

$unpacked = unpack 'd', pack 'Q', 4614256656552045841;;

print $unpacked;;
3.14159265358979

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In Section Seekers of Perl Wisdom