Is the CDL netlist format case-sensitive? Andrew Beckett posted a link that led me to some Pegasus documentation:
https://support.cadence.com/apex/techpubDocViewerPage?path=pegasusref/pegasusref...
21.31/app_pegasus_cdl_ct_CDL_Syntax_Rules_.html

It doesn't say explicitly, but the syntax for a MOS instance line uses L and W, along with lower-case node names:
Code:

M0 d g s b N W=.5 L=.2 M=4 $LDD[LDDN] $NONSWAP