How do I do that?

Recognize that what you have is JSON and use a JSON module :)

#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd pp /;
use JSON qw/ to_json from_json /;
my $str = q{["listliteral",["ListLiteral",["../classSPL_1_1Operator_1_
+1Instance_1_1ExpressionTree_1_1ListLiteral.html",1,"SPL::Operator::In
+stance::ExpressionTree"]]]};
dd( from_json( $str ) );
__END__
[
  "listliteral",
  [
    "ListLiteral",
    [
      "../classSPL_1_1Operator_1_1Instance_1_1ExpressionTree_1_1ListLi
+teral.html",
      1,
      "SPL::Operator::Instance::ExpressionTree",
    ],
  ],
]
[download]

Oh, but you say I switched the single quotes for the double quotes ... :P

Well, what you do have is also perl, so use Safe

#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd pp /;
use Safe;
my $str = q{["listliteral",["ListLiteral",["../classSPL_1_1Operator_1_
+1Instance_1_1ExpressionTree_1_1ListLiteral.html",1,"SPL::Operator::In
+stance::ExpressionTree"]]]};
dd( Safe->new->reval( $str ) );
__END__
[
  "listliteral",
  [
    "ListLiteral",
    [
      "../classSPL_1_1Operator_1_1Instance_1_1ExpressionTree_1_1ListLi
+teral.html",
      1,
      "SPL::Operator::Instance::ExpressionTree",
    ],
  ],
]
[download]