Hi

Is it possible to externally disable warnings within the scope of an already compiled code-block?

That is without manipulating $SIG{__WARN__}³ or to deparse and reevalute the code?

Maybe using some B magic?

motivation

I'm playing around to mimic the for LIST -> variables feature of Perl6¹, but with more syntactic sugar, than splice or natatime can provide.

One of my attempts looks like this and kinda works...

implementation:

<Reveal this spoiler or all in this thread>

model: 

my @a=1..10; # update2

for (1..3) {

  from {@a} loop {
    set my ($a,$b,$c);
    print "(",$a,$b,$c,")";
#    no warnings 'exiting';
#    last;
  };
  
  print "\n";
}
__END__
(123)(456)(789)(10)
(123)(456)(789)(10)
(123)(456)(789)(10)

[download]

...but while using loop-control statements like last works (amazing²) it throws a warning which needs to be silenced.

I could refrain to adding new pseudo statements like xlast() but this break in orthogonality would confuse too much.

Manipulating the sig-handler adds to much overhead, using B::Deparse is somehow risky, cause it's not bug-free.

I think this is of general interest for those playing around with syntactic sugar. :)

Cheers Rolf

( addicted to the Perl Programming Language)

update

¹) from perlcabal 

This can be extended to take more than one element at a time:

    Was:    while (my($age, $sex, $location) = splice @whatever, 0, 3)
+ { ... }
    Now:    for @whatever -> $age, $sex, $location { ... }

(Except the for version does not destroy the array.)

[download]

²) ...and disturbing ... and scaring ... and Perl! ;-)

³) for completeness

$SIG{__WARN__}= sub {
  return if $_[0] =~ /^Exiting subroutine/;
  warn $_[0];
};

[download]

update2

Put initialization of @a to the start to show that the from-loop reinitializes each time, even if broken with last.

In reply to Silencing specific warnings when executing coderef? by LanX

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