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sub safe_print {
    for my $item (@_) {
        print defined $item ? $item : '[undef]';
    }
}

sub safe_print {
    local $_;
    print map { defined $_ ? $_ : '[UNDEF]' } @_;
}

use strict;
use warnings;
...
    print $fh (map { defined $_ ? $_ : '[UNDEF]' } @_);
}
1;

open my $fh, ">", "foo" or die "Can't open foo: $!\n";
my $printer = SafePrinter->new({fh => $fh});
$printer->print("so it goes", undef, 'and it went', "\n");