You're missing the case where $_ is defined in an inner scope.

Compare: 

sub f     {say @_ ? $_[0] : $_}
sub g (_) {say @_ ? $_[0] : $_}

$_ = "outer";
{
    my $_ = "inner";
    f;
    g;
}
__END__
outer
inner

[download]
Lacking the _ prototype, you original code would not work for the case of lexical $_ not in the same scope as the function definition.

In reply to Re^11: How can I avoid code repetition here by JavaFan
in thread How can I avoid code repetition here by rovf

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