"\040" is actually a space, not '(', because 040 octal is 32 decimal.

eval("seek(DATA,0,0;"); doesn't seek to the beginning of your script because it doesn't compile.

my @O_my=<DATA>;
eval("seek DATA,0,0;");
print @O_my;
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prints out only the stuff after __DATA__ because you read from DATA before seeking to the beginning of your script, of course.