$ perl -E '$x = "txt"; sub ref {return $x . "r";}; say &ref($x);'
  txtr
  $ perl -E '$x = "txt"; sub ref {return $x . "r";}; say ref($x);'

  $

##</code><code>##


  $ perl -wE '$x = "txt"; sub ref {return $x . "r";}; say &ref($x);'
  txtr
  $ perl -wE '$x = "txt"; sub ref {return $x . "r";}; say ref($x);'
  Ambiguous call resolved as CORE::ref(), qualify as such or use &
    at -e line 1.

  $

##</code><code>##

  $ perl -wE 'sub say {print "txt\n";}; &say("hello");'
  txt
  $ perl -wE 'sub say {print "txt\n";}; say("hello");'
  hello