With Perl, I wouldn't do raw string parsing; I'd use a Text::CSV (a battle-tested engine). For example, this filters a file foo.csv where `some_header` field is positive (you could also use sort or map or whatever instead of grep):

  perl -MText::CSV=csv -e'my $aoh = csv(in=>"foo.csv",headers=>"auto",keep_headers=>\my @h); @$aoh = grep { $_->{some_header} > 0 } @$aoh; csv(in=>$aoh,out=>*STDOUT,headers=>\@h)'