in reply to Scalar vs. array context w/ join()

The first line has syntax error, print need's a comma or a period between } and "\n". I think you meant this: 
my $columns = [ qw (one two three) ]; # sample data is GOOD
print join "\t",@{$columns}. "\n";
print join ("\t",@{$columns}). "\n";

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I dropped OUT , because it doesn't matter if we are using STDOUT or another handle. So, the first line prints out "3" while the second line prints out the elements of $columns joined by tabs.

What happened to the first line? Precendance my friend, the dot causes @{$columns} to be evaluated in scalar context, leaving join only one element to well, join: "3\n".

That's why i like to use a comma instead: 

print join "\t",@{$columns}, "\n";

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jeffa 

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
F--F--F--F--F--F--F--F--
(the triplet paradiddle)

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Re: (jeffa) Re: Not really obfuscation, but.....
by blakem (Monsignor) on Nov 14, 2001 at 23:40 UTC
    Interesting, I hadn't realized that... This short snippet might illustrate the core issue a bit clearer. 
    #!/usr/bin/perl -wT
use strict;

my @arr = (7,8,9);

print ",, => " , @arr , "\n";  # two commas
print ",. => " , @arr . "\n";  # comma then dot
print "., => " . @arr , "\n";  # dot then comma
print ".. => " . @arr . "\n";  # two dots

=OUTPUT
,, => 789
,. => 3
., => 3
.. => 3

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    -Blake

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(tye)Re2: Not really obfuscation, but.....
by tye (Sage) on Nov 15, 2001 at 02:12 UTC

    Note that your final example:

    print join "\t",@{$columns}, "\n";
    ends the output with "\t\n" instead of just "\n". Note much of a "bug" in this case, but a common mistake that can often have more serious effects.     print join("\t",@{$columns}), "\n";

            - tye (but my friends call me "Tye")
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