perldiag: Rewrap symref error for better splain output

perldiag: Rewrap symref error for better splain output

Before:

    (F) You've told Perl to dereference a string, something which use strict
    blocks to prevent it happening accidentally. See
    "Symbolic references" in perlref. This can be triggered by an @ or $ in a
    double-quoted string immediately before interpolating a variable, for example
    in "user @$twitter_id", which says to treat the contents of $twitter_id
    as an array reference; use a \ to have a literal @ symbol followed by the
    contents of $twitter_id: "user \@$twitter_id".

After:

    (F) You've told Perl to dereference a string, something which
    use strict blocks to prevent it happening accidentally.  See
    "Symbolic references" in perlref.  This can be triggered by an @ or $
    in a double-quoted string immediately before interpolating a variable,
    for example in "user @$twitter_id", which says to treat the contents
    of $twitter_id as an array reference; use a \ to have a literal @
    symbol followed by the contents of $twitter_id: "user \@$twitter_id".