DB<1> @array = qw /foo foobar bar barfoo fobar foobaz /;

  DB<2> x  @array;
0  'foo'
1  'foobar'
2  'bar'
3  'barfoo'
4  'fobar'
5  'foobaz'
  DB<3> $user = "foo";

  DB<4> @a = grep /^\Q$user\E/, @array;

  DB<5> print "@a";
foo foobar foobaz
  DB<7> print join " ", grep !/^\Q$user\E/, @array;
bar barfoo fobar

##</code><code>##

  DB<8> print join " ", grep !/^[$user]/, @array;
bar barfoo
  DB<9> print join " ", grep /^[$user]/, @array;
foo foobar fobar foobaz

##</code><code>##

  DB<27> print join " ", grep /^${user}/, @array;
foo foobar foobaz
  DB<28> print join " ", grep !/^${user}/, @array;
bar barfoo fobar