That won't quite work--braces, {}, are always required for blocks in Perl. So, for instance, the first "if" statement would need to be written as:

if ( substr($F[2],0,3) eq "eth" ) {
    $process=1;
}
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Update: Or to be a bit more "Perlish" you could write:

$process=1 if (substr($F[2],0,3) eq "eth");
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Update 2: Correction of string comparisons, as per Anonymous Monk.