#!/usr/bin/perl -w
BEGIN { $SIG{__WARN__} = sub {
    warn @_ if $_[0] !~ /^Constant subroutine/;
} }
sub FOO() { 23 }
sub FOO() { 42 }

##</code><code>##

#!/usr/bin/perl -w
sub FOO() { 23 }
BEGIN { no warnings 'misc'; undef &FOO if ! @ARGV }
sub FOO() { 42 }