$ perl -we 'my $pi = 4*atan2(1,1);
            print pack "f", $pi' > le-pi.bin
$ od -h le-pi.bin 
0000000 0fdb 4049
0000004

##</code><code>##

$ perl -we 'my $buf;
            read STDIN, $buf, 4;
            my $pi = unpack "f", reverse $buf;
            print "pi=$pi\n";' < le-pi.bin
pi=3.14159274101257

##</code><code>##

  # reverse endianness of first 4-byte float:
  substr( $buf, 0, 4 ) = reverse substr( $buf, 0, 4 );