13foobar@example.com
foo.bar3@example2.com
qwerty-1@dept.example3.com

foobar@example.com
foobar@example2.com
qwerty@dept.example3.com

13foobar@example.com
foo.bar3@example2.com
qwerty-1@dept.example3.com

perl -ne 'my ($user,$host) = split /@/; $user =~ s/[W|d]//g; print $user . "@" . $host;'

cat input | perl -ne 'my ($user,$host) = split /@/; $user =~ s/[W|d]//g; print $user . "@" . $host;'

foobar@example.com
foobar@example2.com
qwerty@dept.example3.com

perl -pe 's/[^a-z]+(?=[^@n]*@)//g'