Another use case could be, that you are simply not
interested in postings about christmas.
- /christmas([-_ ]?(tree|time|eve|pudding))?/
+ /christmas(?:[-_ ]?(?:tree|time|eve|pudding))?/
+
+
+ATTENTION:
+
+It is absolutely important, that you use grouping
+parentheses instead of capturing parentheses!!
+
+Grouping parentheses are:
+
+ (?: )
+
+If you use capturing parentheses, which are
+
+ ( )
+
+it will produce errors and the regex won't work and
+at least your targets will not get collapsed.
+
3)
/\badvent\b/
-The first part if the regex above
+The first part of the regex above
(?<!the )