use strict;
use warnings;

my @values = ( "05F9AD", "F4EC9E", "0005" );
foreach my $value (@values) {
    my $decval = hex($value);
    ($decval >= 0x800000) and $decval -= 0x1000000;
    printf "Hex value 0x%08lx = %ld (decimal)\n", $decval, $decval;
}

__END__

# Output:
Hex value 0x0005f9ad = 391597 (decimal)
Hex value 0xfff4ec9e = -725858 (decimal)
Hex value 0x00000005 = 5 (decimal)