Fix interpreter shift/pop with default @_/@ARGV argument

[fglock]

Problem

shift and pop with no explicit argument failed in interpreter mode:

./jperl --interpreter -E ' say shift ' 123
shift requires array argument at -e line 2, near "say shift "

Root Cause

The parser correctly injects the default array (@main::ARGV at top level, @_ inside a sub) directly as OperatorNode("@", IdentifierNode) on the shift/pop node's operand. However, the bytecode compiler handlers in CompileOperator.java expected the operand to always be wrapped in a ListNode, which is only the case for explicit array arguments like shift \@array.

Fix

Accept operand as either form:

• OperatorNode("@", ...) directly — default @_/@ARGV case injected by parser
• ListNode containing OperatorNode("@", ...) — explicit shift \@array case

Verified

say shift                          # 123  (with arg 123)
say pop                            # 123  (with arg 123)
sub foo { say shift } foo("hello") # hello
my @a=(1,2,3); say shift @a; say pop @a  # 1 / 3