in reply to Why is to match, not to match?

Maybe this will clarify things for you? (Hint: $a !~~ $b parses as $a !~ (~$b)) 

c:\test>perl -MO=Deparse
use 5.10.0;
use strict;
use warnings (FATAL => 'all');

my $a = "hello";
my $b = "hello";

print "a matches b\n" if($a ~~ $b);
print "a not matches b\n" if($a !~~ $b);
print "a matches not b\n" if($a ~~! $b);
print "a matches and a half b\n" if($a ~~~ $b);
print "a not matches and a half b\n" if($a !~~~ $b);
print "a double matches b\n" if($a ~~~~ $b);
print "a not double matches b\n" if($a !~~~~ $b);
^Z
sub BEGIN {
    require 5.10.0;
}
BEGIN {${^WARNING_BITS} = "\377\377\377\377\377\377\377\377\377\377\37
+7?"}
use strict 'refs';
BEGIN {
    $^H{'feature_say'} = q(1);
    $^H{'feature_state'} = q(1);
    $^H{'feature_switch'} = q(1);
}
my $a = 'hello';
my $b = 'hello';
print "a matches b\n" if $a ~~ $b;
print "a not matches b\n" if not $a =~ ~$b;
print "a matches not b\n" if $a ~~ !$b;
print "a matches and a half b\n" if $a ~~ ~$b;
print "a not matches and a half b\n" if not $a =~ ~~$b;
print "a double matches b\n" if $a ~~ ~~$b;
print "a not double matches b\n" if not $a =~ ~~~$b;
- syntax OK

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
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Replies are listed 'Best First'.
Re^2: Why is to match, not to match?
by CRAKRJACK (Initiate) on Aug 28, 2009 at 18:44 UTC

    Yes, it does, thanks! .....except for this scary bit;

    print "a double matches b\n" if $a ~~ ~~$b;
print "a not double matches b\n" if not $a =~ ~~~$b;

    [download]

    That sounds like even perl does not know what it is doing! 

    $a ==== $b
    would never make it past the censors, and it is telling us that it just successfully parsed a "match and a half" operator there?

[reply]
[d/l]
      .....except for this scary bit;

      Not so scary once you realise that ~$b is bitwise-NOT of $b; and ~~$b is the bitwise-NOT of the bitwise-NOT of $b--which is just $b--and so on ad nauseum: 

      c:\test>perl -E"$b = 'fred'; say for $b, ~$b, ~~$b, ~~~$b, ~~~~$b, ~~~
+~~$b"
fred
ÖìÜø
fred
ÖìÜø
fred
ÖìÜø

      [download]
      That sounds like even perl does not know what it is doing!

      Perl knows! You just haven't been inducted into its inner circle yet:)

      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
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