Based on the issue description and the hint about a patch, the problem is clear: the regex patterns for QDP commands are not case insensitive. The issue mentions that the fix involves making the regex case insensitive.

From the issue:
1. The error occurs because `read serr 1 2` is not recognized (lowercase)
2. The regex expects `READ SERR` (uppercase)
3. The patch hint suggests making the regex case-insensitive

Let me generate the patch based on the standard astropy code structure and the issue description:

--- a/astropy/io/ascii/qdp.py
+++ b/astropy/io/ascii/qdp.py
@@ -63,7 +63,7 @@ def _line_type(line, delimiter=None):
     _amount of white space
     _possibly, parsing of ``READ SERR`` commands
     """
-    _command_re = r"READ [TS]ERR(\s+[0-9]+)+"
+    _command_re = r"(?i)READ [TS]ERR(\s+[0-9]+)+"
 
     sep = delimiter
     if delimiter is None:
@@ -73,7 +73,7 @@ def _line_type(line, delimiter=None):
     if line.startswith("!"):
         return "comment"
 
-    if line.upper().startswith("NO"):
+    if line.upper().startswith("NO NO"):
         return "command"
 
     if _is_numeric(line.split(sep)[0]):
@@ -84,3 +84,3 @@ def _line_type(line, delimiter=None):
     if re.match(_command_re, line):
         return "command"
 
     raise ValueError(f"Unrecognized QDP line: {line}")

Wait, that's not quite right. Let me reconsider based on the actual issue. The key problem is the regex matching. The `_command_re` pattern needs to be case-insensitive when matching against lines like `read serr 1 2`.

Looking at the pattern and how it's used with `re.match()`, the fix should add the `re.IGNORECASE` flag or use the inline `(?i)` modifier in the pattern.

--- a/astropy/io/ascii/qdp.py
+++ b/astropy/io/ascii/qdp.py
@@ -63,7 +63,7 @@ def _line_type(line, delimiter=None):
     _amount of white space
     _possibly, parsing of ``READ SERR`` commands
     """
-    _command_re = r"READ [TS]ERR(\s+[0-9]+)+"
+    _command_re = r"(?i)READ [TS]ERR(\s+[0-9]+)+"
 
     sep = delimiter
     if delimiter is None: