To be honest, I've never used pegs in Nim before but looking at it's source, it
has MaxSubpatterns = 20. So, I guess either you can define matches as
newSeq[string](20) or you can use this,
if fixedString =~ peg"cd\s+{\D}\:":
echo matches[0]
Runwithout defining matches at all, because it injects matches variable itself, if there is none at current scope.
