or download this
>perl -MEncode -e"print encode 'UTF-8', qq{use utf8; my \$x='a\xE1axBy
+'; \$x =~ /(.*?)x(A*)y/; }" | perl
Malformed UTF-8 character (unexpected continuation byte 0xa1, with no
+preceding start byte) in pattern match (m//) at - line 1.