Re^4: looking for a good idiom: return this if this is true

if (thatroutine()) {return $_}
$_ isn't getting set there. Are you expecting the variable to be psychic?

No, I'm not expecting that. I tested this with a one-liner prior to posting, I swear. Problem is, I just tried re-entering that one-liner prior to posting my proof here and.... It doesn't work. I suppose I must have screwed that up somehow, the first time around. I'm not entirely clear on how $_ works.

--
Linux, sci-fi, and Nat Torkington, all at Penguicon 3.0
perl -e 'print(map(chr,(0x4a,0x41,0x50,0x48,0xa)))'

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Re^5: looking for a good idiom: return this if this is true by merlyn (Sage) on Mar 07, 2005 at 19:25 UTC
$_ is set by very few things: An explicit assignment ($_ = 35). The implicit setting for a while() loop reading from a filehandle: `while (<HANDLE>) { ... } # same as ... while (defined($_ = <HANDLE>)) { ... }` [download] The implicit variable of a foreach loop: `foreach (@list) { ... } # same as foreach $_ (@list) { ... }` [download] The implicit variable of a grep/map block (added after prodding, sorry): `$count = grep { BLOCK } LIST; @result = grep { BLOCK } LIST; @result = map { BLOCK } LIST; map { BLOCK } LIST; # invalidates your warranty` [download] I think that's it. I don't recall anything else that can set the value. Lots of operations can alter the value, like chomp or s///. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply] [d/l] [select]

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Re^5: looking for a good idiom: return this if this is true
by merlyn (Sage) on Mar 07, 2005 at 19:25 UTC

An explicit assignment ($_ = 35).

The implicit setting for a while() loop reading from a filehandle:

while (<HANDLE>) { ... } # same as ...
while (defined($_ = <HANDLE>)) { ... }
[download]

The implicit variable of a foreach loop:

foreach (@list) { ... } # same as foreach $_ (@list) { ... }
[download]

The implicit variable of a grep/map block (added after prodding, sorry):

$count = grep { BLOCK } LIST;
@result = grep { BLOCK } LIST;
@result = map { BLOCK } LIST;
map { BLOCK } LIST; # invalidates your warranty
[download]

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

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