How to match "no" in a string using prxmatch but not "not" - regex

Question

I am pulling out survey participants comments from a dataset using prxmatch in SAS EG 7.1. There are a lot of comments that start with "No", it might just be no on its own or it might say no problems etc. I only want to filter these out if the string starts with "no", and not if "no" is contained elsewhere in the string so I have included the ^ metacharacter but I noticed some comments are being filtered out if they have "not" in them so I include \b after no for the word boundary however it is still filtering out strings that have "not" or "no" anywhere within the string.
Examples of what should match:
"No problems" "No"
Examples of what should NOT match:
"His name is STEVE not SPEVE" "I was mostly fine but I was not expecting to get a headache"
How do I stop this from happening? I've included my code, any help would be great.
data cclhd hnelhd islhd nbmlhd seslhd swslhd slhd wslhd mnclhd nnswlhd wnswlhd;
set work.schools_dataset;
where Comments ne " ";
if prxmatch ("m/^no\b|^nil|^none|^nop|all good|na|n\/a|n\.a/i",Comments) = 0 ;
keep ParticipantID FirstName Mobile VaxDate OperationID Venue Comments;
if operationid=108 then output work.cclhd;
else if operationid=109 then output work.hnelhd;
else if operationid=110 then output work.islhd;
else if operationid=111 then output work.nbmlhd;
else if operationid=113 then output work.seslhd;
else if operationid=114 then output work.swslhd;
else if operationid=115 then output work.slhd;
else if operationid=116 then output work.wslhd;
else if operationid=118 then output work.mnclhd;
else if operationid=120 then output work.nnswlhd;
else if operationid=122 then output work.wnswlhd;
run;

Answer 1

Try:
data cclhd hnelhd islhd nbmlhd seslhd swslhd slhd wslhd mnclhd nnswlhd wnswlhd;
set work.schools_dataset;
where Comments ne " ";
if prxmatch("/^no\b/i",comments) = 0;
keep ParticipantID FirstName Mobile VaxDate OperationID Venue Comments;
if operationid=108 then output work.cclhd;
else if operationid=109 then output work.hnelhd;
else if operationid=110 then output work.islhd;
else if operationid=111 then output work.nbmlhd;
else if operationid=113 then output work.seslhd;
else if operationid=114 then output work.swslhd;
else if operationid=115 then output work.slhd;
else if operationid=116 then output work.wslhd;
else if operationid=118 then output work.mnclhd;
else if operationid=120 then output work.nnswlhd;
else if operationid=122 then output work.wnswlhd;