use Path::Class qw( file );

print(
    file('A:\\B.CD(E)~!@#$%^&\\E\\F.txt')
        ->relative('A:\\B.CD(E)~!@#$%^&'),
    "\n"
);

##</code><code>##

use File::Spec::Functions qw( abs2rel );

print(
    abs2rel('A:\\B.CD(E)~!@#$%^&\\E\\F.txt',
        'A:\\B.CD(E)~!@#$%^&'),
    "\n"
);