in reply to Forward declaration of subs

Is there any practical application of forward declaration of subroutines?

Yes. If you have mutually recursive subroutines -- sub a calls sub b; and sub b calls sub a; -- then you need to forward declare one of them to pass strict, if you want to avoid using parens.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

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Re^2: Forward declaration of subs
by LanX (Saint) on Oct 12, 2013 at 00:24 UTC
    > mutually recursive subroutines ... if you want to avoid using parens.

    As an illustration, the following doesn't work cause &b is unknown when &a is compiled.

    Without strict b will be converted to string "b" and returned. (strict prohibits this behaviour of barewords.)

    lanx@nc10-ubuntu:/tmp$ perl
sub a { print "a$level "; b if $level-- };
sub b { print "b$level "; a if $level-- };
$level=5;
print"\n";
a;
print"\n";
b;
__END__

a5 
b4 a3

    [download]

    with forward declaration

    lanx@nc10-ubuntu:/tmp$ perl
sub b;
sub a { print "a$level "; b if $level-- };
sub b { print "b$level "; a if $level-- };
$level=5;
print"\n";
a;
__END__

a5 b4 a3 b2 a1 b0

    [download]

    Cheers Rolf

    ( addicted to the Perl Programming Language)

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      Better addressed to the OP.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]

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