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

I was translating morse code, and each centered-point was translated to two (not one) ascii dots. Can anybody explain?
use warnings;
use strict;

$_ = '·|·';
print y/·/./r, "\n";
print s/·/./gr, "\n";

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OUTPUT:
..|..
.|.

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Replies are listed 'Best First'.
Re: y/·/./ gives two points instead of one
by ikegami (Patriarch) on Nov 16, 2015 at 21:38 UTC

    You think you have 

    $_ = '·|·';
print y/·/./r, "\n";
print s/·/./gr, "\n";

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    but you actually have 

    $_ = '·|·';
print y/·/./r, "\n";
print s/·/./gr, "\n";

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    This is because you treated the file as UTF-8 when you viewed it, but you didn't tell Perl to do the same by adding use utf8;.

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      Thanks for explanation!
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Re: y/·/./ gives two points instead of one
by LanX (Saint) on Nov 16, 2015 at 21:21 UTC
    > Can anybody explain?

    use utf8 ! :)

    Cheers Rolf
    (addicted to the Perl Programming Language and ☆☆☆☆ :)
    Je suis Charlie!

    update

    Without utf8 flag you are forcing perl to transliterate a 2 byte character to a 1 byte character.

    My interpretation is that this 1 byte char is doubled to keep the counters in sync.¹

    update

    same effect here 

    use warnings;
use strict;
#use utf8;

$_ = '§|§';

print y/§/$/r, "\n";

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    Careful with such experiments, I was able to make my Perl (5.14) coredump

    update

    ¹) ikegami's explanation is better, you are transliterating the first and second byte for · separately to .

      DB<123> unpack 'H*','·'
 => "c2b7"

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    Got confused about the tr flags and their defaults.

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