build-namelist hangs (infinite loop) on #-commented line in user_nl_cam #1701

What happened?

A line in user_nl_cam commented with # instead of ! causes build-namelist to hang with no output when it follows a variable assignment. Found on cam6_4_203.

What are the steps to reproduce the bug?

&a x=1
#y = 'f.nc'
/

Passing this through Build::Namelist->new never returns. In _parse_next (bld/perl5lib/Build/Namelist.pm), in the varorvalue state neither the variable nor the value regex consumes the # line, and $expect is never set to error, so _parse loops on the same text indefinitely.

If the # line is instead the first line after the group name, a clean "expect a variable" error is raised, so the expected behavior is the same error in the varorvalue case. Under CIME this appears as case.build stalling at "Create namelist for component cam."

What CAM tag were you using?

my stormspeed branch based off of cam6_4_203

What machine were you running CAM on?

CISL machine (e.g. derecho)

What compiler were you using?

Intel

Path to a case directory, if applicable

No response

Will you be addressing this bug yourself?

Any CAM SE can do this

Extra info

I was running on my StormSPEED branch but haven't modified any of the perl code.