Because

print hex '428C0000';
1116471296
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The original input was in hex, you are printing decimal.

Thanks, but the thing which hurt me is the 'no-symmetry':



$float= unpack "f", pack "L", 0x428C0000;
# $float is 70
$float= sprintf("%lx", unpack "L", pack "f", 70 );
print $float; # print 428C0000
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I take this as a fact but I don't understand why the exact
opposite expression doesn't give back the original data:


$is_not_hex = unpack "L", pack "f", 70 ;
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The reason has nothing to do with pack or unpack, it is the same reason that printing a hex constant doesn't print exactly what you see.

print 0x428c0000;

1116471296
[download]

Perl automatically converts hex values (as indicated by 0x...) to it internal (binary) representation when parsing the source code. It becomes just another perl number.

Whenever perl prints out a number, it prints the ascii representation of it's decimal value, unless you specifically state that you want it printed in some other form. Ie. using printf or sprintf or similar.

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