please read perlintro, Modern Perl and/or one of the other tutorials. you're doing wrong almost everything what could possibly go wrong =)

you are not using warnings and strict.
the element in @List will contain the string "C:SernameSources".
you are trying to use $_ but $arrchar is the variable you want to do the matching on.
by saying $_ = /.../ you are assigning to $_. you have to say $arrchar =~ /\\/