Implementation requirements

Perl 6's list and iterator model must be able to handle

• laziness ↔ eagerness
• finite ↔ infinite
• interpolating ↔ non-interpolating
• flattening ↔ structure preserving
• bound vs unbound
• aliasing (lists, parcels) vs copying (arrays)

Oh, and also

• the programmer shouldn't be burdened with details
• it's all generally dynamic
• it has to be really fast