system() is not the right function for the purpose of capturing output. Consider qx// (aka `backticks`) or open() for that job.

I don't know if grepping for "ERROR" in the command's STDOUT would suffice, you should be able to specify that ;)

open my $pipe , '-|' , 'sqlplus user/pass @test.sql'
    or die "hmm? $!";

while( <$pipe> ){
    print if /error/i
}

close $pipe or die "hmhmm? $!";
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