[^~\x22]+
.*
Ignore strings that start with the label “abc_”.
Use a negative look-ahead assertion:
^(?!abc_).+
Or, use a negative look-behind assertion:
(^.{1,3}$|^.{4}(?<!abc_).*)
Or, use plain old character sets and alternations:
^([^a]|a($|[^b]|b($|[^c]|c($|[^_])))).*
Use a negative lookbehind assertion:
^[/\w\.-]+(?<!\.html)$
or, use a lookahead:
^(?!.*\.html$)[/\w\.-]+$
or, another use of a lookahead assertion:
/((?!\.html$)[/\w.-])+/
NOTE:
To force it to match the entire string, anchor the entire pattern with ^ at the start and $ at the end; otherwise it is free to only match a portion of the string. With this change, it becomes:
/^((?!\.html$)[/\w.-])+$/