while(<>) in perl 5.22

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

So a script I wrote long ago has stopped working somewhere between perl 5.x and 5.22.
myscript.pl

#!/usr/bin/perl
use strict;

while (<>) {
# do stuff with each argument given and spit out a sting.
# this example I'll just do
print;

}
[download]

Now when I run it

$> ./myscript.pl foo bar baz
Can't open foo: No such file or directory at ./sp2comma.pl line 13.
Can't open bar: No such file or directory at ./sp2comma.pl line 13.
Can't open baz: No such file or directory at ./sp2comma.pl line 13.
[download]

The expected result is of course

$> ./myscript.pl foo bar baz
foobarbaz
[download]

Has something happened? Why is while (<>) not doing what it use to? How do I get the old behavior? Thanks in advance.

Comment on while(<>) in perl 5.22 Select or Download Code

Replies are listed 'Best First'.
Re: while(<>) in perl 5.22 by toolic (Bishop) on Nov 14, 2016 at 19:54 UTC
I reproduce your undesired behavior on 5.16. To get your desired output in this instance, replace `while (<>)` with `for (@ARGV)` See also perlop	[reply] [d/l] [select]
Re: while(<>) in perl 5.22 by dsheroh (Monsignor) on Nov 15, 2016 at 08:33 UTC
Has something happened? Nope. Why is `while (<>)` not doing what it use to? It's doing the same thing as it has since at least 1999, when I started using Perl, and probably always has. How do I get the old behavior `<>` reads either from files named as command-line arguments or from `STDIN`. It does not, and never has, returned the literal command-line arguments themselves. If you want to access the literal command-line arguments, you can find them in the array `@ARGV`. e.g.: `$ perl -E 'for (@ARGV) { say $_ }' foo bar baz foo bar baz` [download]	[reply] [d/l] [select]
Re^2: while(<>) in perl 5.22 by haukex (Bishop) on Nov 15, 2016 at 09:18 UTC
Hi dsheroh, It's doing the same thing as it has since at least 1999, when I started using Perl, and probably always has. I just tested it and can confirm what you wrote for all Perl releases from 5.002 (1996) to v5.24. Regards, -- Hauke D	[reply]
Re: while(<>) in perl 5.22 by choroba (Archbishop) on Nov 14, 2016 at 21:46 UTC
> somewhere between perl 5.x and 5.22 Interesting. The diamond operator `<>` is documented to behave this way for x=0.4 (I wasn't able to find older references easily). ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]
Re^2: while(<>) in perl 5.22 by BillKSmith (Monsignor) on Nov 14, 2016 at 23:04 UTC
Neither result is consistent with my understanding of the 5.22 documentation. `while (<>) { ... # code for each line } is equivalent to the following Perl-like pseudo code: unshift(@ARGV, '-') unless @ARGV; while ($ARGV = shift) { open(ARGV, $ARGV); while (<ARGV>) { ... # code for each line } }` [download] I would expect the open to fail silently.(There is no explicit test for errors.) The read on the unopened filehandle should return a false value. The loop would terminate without ever executing the print statement. Bill	[reply] [d/l]
Re^3: while(<>) in perl 5.22 by choroba (Archbishop) on Nov 14, 2016 at 23:25 UTC
The documentation also says there's a difference, and you can easily see there is: `~ $ perl -e '1 while <>' non-existent-file Can't open non-existent-file: No such file or directory at -e line 1.` [download] ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]


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