---input---
puts a-$foo-b
puts ${foo-bar}

---tokens---
'puts'        Name.Builtin
' '           Text.Whitespace
'a-'          Text
'$foo'        Name.Variable
'-'           Operator
'b'           Text
'\n'          Text

'puts'        Name.Builtin
' '           Text.Whitespace
'${foo-bar}'  Name.Variable
'\n'          Text
