DB<106> sub avoid (&;@) { my $code=shift; my $msg = $code->(@_); die $msg if $msg; } DB<107> avoid { "Got extra Z: @_\n" if @_ >1 } my @v = keys %h; Got extra Z: a b DB<108> %h=(a=>1) => ("a", 1) DB<109> avoid { "Got extra Z: @_\n" if @_ >1 } my @v = keys %h; DB<110>