With a clever strategy it's possible to significantly limit the number of possible chunks to check!

Simply start checking the most indented line and successively add surrounding lines.

for my $foo (@foo) {                          # 8 fails
    for my $bar (@$foo) {                     # 6 fails
        push @{ $self->{results} },           # 5 works
            {                                 # 3 fails
                baz => foo( $bar->{baz},      # 2 works
                            $bar->{quux}[1] ) # 1 fails
            };                                # 4 works
    }                                         # 7 works
}                                             # 9 works
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like this the overhead for identifying n lines of code is (statistically) at most linear!

UPDATE: And it's still possible to rely on the existence of trailing semicolons or braces before running a syntax check.