If you don't fancy reading the excellent perlrun to find out what the flags do, then just use B::Deparse to find out:

$ perl -MO=Deparse -F'"' -lE 'say $F[$_ * 2 + 1] for 0 .. $#F/2'
BEGIN { $/ = "\n"; $\ = "\n"; }
use feature 'current_sub', 'bitwise', 'evalbytes', 'fc', 'postderef_qq
+', 'say', 'state', 'switch', 'unicode_strings', 'unicode_eval';
LINE: while (defined($_ = readline ARGV)) {
    chomp $_;
    our @F = split(/"/u, $_, 0);
    say $F[$_ * 2 + 1] foreach (0 .. $#F / 2);
}
-e syntax OK
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(Updated to match the original code)