or download this
c:\test>junk9
'Error 123 on SystemA file not found error' does match (?-xism:Err
+or 123 on (\S+) file not found error)
...
'Error 124 on User3:FileC no space left' does not match (?-xism:Error
+123 on (\S+) file not found error)
'Error 124 on User3:FileC no space left' does match (?-xism:Error
+124 on (\S+):(\S+) no space left)