$ perl -MCSelTest -MData::Dump -E 'dd CSelTest::parse(q{ [attr] })'

##</code><code>##

Perl v5.20.0 required--this is only v5.18.0, stopped at CSelTest.pm line 3.
BEGIN failed--compilation aborted at CSelTest.pm line 3.
Compilation failed in require.
BEGIN failed--compilation aborted.

##</code><code>##

panic: memory wrap at CSelTest.pm line 107.
Compilation failed in require.
BEGIN failed--compilation aborted.

##</code><code>##

Switch (?(condition)... not terminated in regex; marked by <-- HERE in m/
          (?&ATTR_SELECTOR) (?{ $_ = $^R->[1] })

          (?(DEFINE)

          ...

          ) # DEFINE
   <-- HERE / at CSelTest.pm line 107.
Compilation failed in require.
BEGIN failed--compilation aborted.

##</code><code>##

% perl -I. -Ilib -MCSelTest -MData::Dump -E'dd( CSelTest::parse_csel(q{ [attr=1] }) )'
[[{ name => "attr" }], "eq", 1]

##</code><code>##

% perl -I. -Ilib -MCSelTest -MData::Dump -E'dd( CSelTest::parse_csel(q{ [attr=1] }) )'
[[{ name => "attr" }], "=", 1]