Re: Re: GetOpt::Long usage style

\(my $verbose='');

my returns what has been declared. (Although the behaviour of it as a function is a little interesting, I dont think it can be prototyped, and I can't find complete documentation for it off hand.) The parenthesis required because the precedence of the assignment operator causes

GetOptions(x=>my $x=1,y=>my $y);
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to be parsed something like

GetOptions('x',(my $x=1,y=>my $y));
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which is a syntax error. They aren't required when the variable isn't initialized as part of the my. Also I personally think that they add visual calrity when the reference to the variable is taken. Since the my returns the variable declared (as an lvalue) we can take a reference to it with \. The reference operator \ can technically go inside the parens or outside in this case as

\($x,$y,$z)
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is shorthand for

(\$x,\$y,\$z)
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Hope that clarifys things. ;-) Er, and yes. You analysed it correctly. :-)

A couple of related tricks are:

my $txt="Foo bar";
(my $clean=$txt)=~s/oo/u/g;

open my $fh,"File" or die "File $!";

if (my ($x,$y,$z)=/A(..)(..)(..)Z/) { }
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---
demerphq

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Re^3: GetOpt::Long usage style by OneTrueDabe (Acolyte) on May 08, 2014 at 16:00 UTC
I know this is ancient, but since it's high on the Google hit list, I wanted to mention one thing... This very cool trick does not work for @arrays. :-( This: `use Getopt::Long; GetOptions( 'single=s' => \(my $single = ''), 'multi=s' => \(my @multi = ()), );` [download] does NOT DWIM. According to "perlref": As a special case, "\(@foo)" returns a list of references to the contents of @foo, not a reference to @foo itself. I tried all kinds of permutations, and the best I could come up with was: `use Getopt::Long; GetOptions( 'single=s' => \(my $single = ''), 'multi=s' => do { use vars '@multi'; \@multi }, );` [download] which, isn't quite as clean, IMHO. (It DOES, however, keep the variable declarations and command-line options on the same line, at least, so you don't have to make changes in multiple places when adding new options. shrug)	[reply] [d/l] [select]
Re^4: GetOpt::Long usage style (\my @a) by tye (Sage) on May 09, 2014 at 00:37 UTC
`use Getopt::Long; GetOptions( 'single=s' => \(my $single = ''), 'multi=s' => \my @multi, );` [download] If you want to provide a non-empty default value, one way is: `use Getopt::Long; GetOptions( 'single=s' => \(my $single = ''), 'multi=s' => grep { @$_ = ('a','b') } \my @multi, );` [download] - tye	[reply] [d/l] [select]
Re^4: GetOpt::Long usage style by demerphq (Chancellor) on Apr 11, 2016 at 17:22 UTC
Besides what tye said in Re^4: GetOpt::Long usage style (\my @a), you can just use an arrayref instead. Obviously the reference operator \ required for scalars can be omitted. `'multi=s' => (my $multi = [1..3]),` [download] Same for a hash/hashref. Admittedly it is not quite the same as what one would expect from `'multi=s' => (\my @multi = (1..3)),` [download] Which throws an error, which I think is arguably an error in Perl. BTW, sorry it took me so long to reply, and thanks for adding your point. --- $world=~s/war/peace/g	[reply] [d/l] [select]


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