Use caseInsensitivePattern to match text regardless of whether the text is upper-case or lower-case.

Create txt as a string with "abc" repeated in a mixture of upper- and lower-case. Create a pattern, pat, that matches the literal "abc". Extract the pattern.

txt = "abc ABC AbC";
pat = "abc";
extract(txt,pat)

ans = 
"abc"

Make pat case insensitive using caseInsensitivePattern. Extract the new pattern.

pat = caseInsensitivePattern(pat);
extract(txt,pat)

ans = 3x1 string
    "abc"
    "ABC"
    "AbC"

Use caseInsensitivePattern to enforce case insensitivity in case-sensitive functions.

Create a string of lowercase letters. Create a pattern that matches uppercase "ABC". When used in a case-sensitive function, pat does not match txt.

txt = "abc";
pat = "ABC";
contains(txt,pat,'IgnoreCase',false)

ans = logical
   0

Use caseInsensitivePattern to enforce case insensitivity in matching for pat even when used as the input for a case-sensitive function.

pat = caseInsensitivePattern(pat);
contains(txt,pat,'IgnoreCase',false)

ans = logical
   1