This should work on many platforms for the example data you gave:

my $float= unpack "f", pack "L", 0x428C0000;
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(assuming the value you wanted was the nice-looking "70").

but I'm not sure how to reconcile the terms "in ASCII" vs. "e.g. 0x428C0000". Perhaps you have a string like "0x428C0000":

my $string= "0x428C0000";
my $float= unpack "f", pack "L", hex $string;
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or perhaps you have a string of bytes whose hex values are 42, 8C, 00, and 00:

my $string= "\x42\x8C\x00\x00";
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in which case you could pick between these two, depending on whether the source and destination systems are the same or different endian:

$float= unpack "f", $string;
$float= unpack "f", scalar reverse $string;
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or you could use use two steps to auto-handle the receiving ends endianness (since your example data appears to show me the endianness of the source):

my $string= "\x42\x8C\x00\x00";
my $float= unpack "f", pack "L", unpack "N", $string;
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