I first load the hash with only the test name that i'm interested to extract then use the code below to do the actual extraction into a text file.
i've ran just a while loop going through the file, and it takes about 25secs, and when i ran it through my code below, it takes about 52secs.
any other helpful advice? thanks~

## extract all the param values from the stdf
sub get_paramValue
{
    my ($stdf,$lot,$oper,$sum,%param_flag) = @_;
    my ($output);

    print "Running with stdf:$stdf.\n";
    &log("get_paramValue","Running with stdf:$stdf.");

    if(-e $stdf){
        ## create the output file name, similar to the stdf name but w
+ith .log ext
        $output = $outputdir.$lot."_".$oper."_".$sum.".log";

        open(OUT, ">$output") or &log("get_paramValue","Can't write to
+ output: $output");
        print OUT "tname,idx,param_val\n";

        open(STDF, $stdf) or &log("get_paramValue","Die can't read fro
+m stdf:$stdf.");
        my (@tmp,$testname,$testFound,$paramVal,$unit_count);
        while(<STDF>){
            if(/3_prtnm_/){
                @tmp = split(/3_prtnm_/);
                $unit_count = &trim($tmp[1]);
            }
            elsif(/2_tname_/){
                @tmp = split(/2_tname_/);
                $testname = &trim($tmp[1]);
                if(exists $param_flag{$testname}){
                    $testFound = 1;
                }
            }
            elsif($testFound){
                if(/2_mrslt_/){
                    @tmp = split(/2_mrslt_/);
                    $paramVal = &trim($tmp[1]);
                    print OUT "$testname,$unit_count,$paramVal\n";
                    $testFound = 0;
                }
            }
        } ## END while
        close(STDF);
        close(OUT);
    } ## END IF
    
    return $output;
} ## end sub
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