Looks like it cannot be used with Str interpolation. I'm afraid this is a bug, but not 100% sure.

Fan Shell v1.0.41 ('?' for help)
fansh> "a,b".split(',').each |elt| { echo("$elt") }
a
b
fansh> "a,b".split(',').each { echo("$it") }
ERROR(34): Expected identifier after $
fansh> "a,b".split(',').each { echo(it) }
a
b
fansh>

Promoted to ticket #551 and assigned to brian

yeap, that is a bug

Ticket resolved in 1.0.42