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Re^5: What is true and false in Perl?

by jdporter (Canon)
on Oct 18, 2012 at 15:25 UTC ( #999756=note: print w/replies, xml ) Need Help??


in reply to Re^4: What is true and false in Perl?
in thread What is true and false in Perl?

The same thing tobyink and tye said, though more obtusely and snarkily.

Here's another example:

tie my $var, 'Some::BlackBox::Module'; $var = "45"; if ( $var ) { print "var is true\n" } # doesn't print! WTF?

The mere fact that an expression evaluates to a true value in scalar context doesn't mean it is true.

tie and overload are among the user-accessible features which can muddy the true/false waters.

An example like this should make the principle more obvious:

my $obj = ObjectWithLotsOfOpaqueStructure::AndLotsOfHiddenState->new( -use_overloading => 1, ); if ( $obj ) { print "obj is 'true'.\n"; # What does this even mean? # Maybe obj is an iterator with another available item? }

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[LanX]: not my code ...
[choroba]: yeah, sounds like one of the strings is not flagged as UTF-8
[choroba]: which usually means its input wasn't handled correctly
[Corion]: choroba: Yeah, I think that would be the good solution
[LanX]: I suspect the first string which comes from the DB ...
[LanX]: ... but this part is already in production for a year now
[Corion]: LanX: The "good" approach here would be to use the appropriate DBI parameters to make the driver decode strings properly. But that will have a ripple-on effect of messing up all the places where manual decoding happens ;)
[LanX]: which means albeit being broken UTF8 it'll be handled correctly
[LanX]: and the problem only occurs since we changed the emails to base64
[LanX]: my main problem will be to cnvince my colleagues that our productive code is broken oO ... so in the end I will just make a workaround :-/

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