Embedded variable assignments inside local declarations

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

This is allowed and works:

    local ($a=1, $b=2, $c=3);
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But this isn't and gives an error:

    my ($a=1, $b=2, $c=3);
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The following is what I would normally use myself:


    my ($a, $b, $c) = (1,2,3);
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I have seen the first construct used in someone else's code, but I'm not sure if it is a Perl crime or not - anyone know?

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Re: Embedded variable assignments inside local declarations by broquaint (Abbot) on Jan 26, 2003 at 17:03 UTC
This is allowed and works ... It parses, but doesn't do what you might think it does e.g `$foo = "a string"; { local( $foo = "localised" ); print $foo,$/; } print $foo,$/; __output__ localised localised` [download] The output from `B::Deparse` also gives it away (assuming above code passed through `perl -MO=Deparse,-p -`) `($foo = 'a string'); { ($foo = 'localised'); print($foo, $/); } print($foo, $/); - syntax OK` [download] HTH `_________ broquaint`	[reply] [d/l] [select]
•Re: Embedded variable assignments inside local declarations by merlyn (Sage) on Jan 26, 2003 at 17:07 UTC
Oddly enough, this would work fine, although I'd question it in a code review: `my $a = 1, my $b = 2, my $c = 3;` [download] Why not just change those commas to semis and be done with it? -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l]
Re: •Re: Embedded variable assignments inside local declarations by pg (Canon) on Jan 26, 2003 at 19:39 UTC
`$a = 1, $b = 2, $c = 3;` works, and that's exactly why `my $a = 1, my $b = 2, my $c = 3; would work.` Although it looks odd, but from a Perl internal view, it is the same animal as the following (,which we see from day to day): `foreach $line (@lines) { ... }` [download] works, that's why `foreach my $line (@lines) { ... }` [download] Basically, Perl allows you to my variables on fly. One more example for the same animal: `for (my $i = 1; $i < 10; $i ++) { print $i; }` [download]	[reply] [d/l] [select]
Re: Embedded variable assignments inside local declarations by integral (Hermit) on Jan 28, 2003 at 19:55 UTC
The difference has probably been caused by the fact that local and my were implemented at different times, and so local takes a list expression, while my is restricted to just plain unqualified variable names. In addition local is more flexible than my, since my only allows unqualified variables, whilst local allows things like hash elements (more than just variables anyways). -- integral, resident of freenode's #perl	[reply]