kos has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks:

I have a subroutine that I call several times in my program. For some reason, when I call it with no arguments at one point @_ is set to ('main'). What's going on? This occures from the initiation of the subroutine. it's driving me insane..
I haven't been able to reproduce the results with test programs, but here's the line from which the subroutine is called, with a surrogate subroutine for all it's worth... 

(( &token( "next", "marker" ))[0] eq ';') && &token;

sub token{
    print "args: @_\n";

    return 1;
}

sub error{
    return;
}

[download]
much thanks.

20040105 Edit by ysth: p, br, and code tags

Replies are listed 'Best First'.
Re: Has Perl gone completely insane on me?
by ikegami (Patriarch) on Jan 06, 2005 at 06:40 UTC

    When you use & and no arguments, @_ is preserved.

    sub func { print(scalar(@_), $/); }

@_ = qw(a b c);

&func;        # 3
func();       # 0
func;         # 0

&func(1, 2);  # 2
func(1, 2);   # 2
func 1, 2;    # 2

    [download]

    There's rarely any need to use the ampersand notation. I think you shouldn't use it unless necessary.

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[d/l]
      There's rarely any need to use the ampersand notation. I think you shouldn't use it unless necessary.
      Some people feel more comfortable using &. It leads to less action at a distance (where perl parses differently depending on whether it's already seen a sub declaration). But if you do choose to use &, always use () with it.
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