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The stupid question is the question not asked

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Another similarity between perl and shell (common to C as well), is that the second expression will not be evaluated at all if the first expression "answers the question". This matters when the second expression has side effects. Some trivial examples:
sub f0 { return 0 } sub f1 { return 1 } if (( my $x = f1() ) && ( my $y = f1() )) # true, and both variables are set to 1 if (( my $x = f0() ) && ( my $y = f1() )) # false, $x is set to 0, $y is undef if (( my $x = f0() ) || ( my $y = f1() )) # true, $x is set to 0, $y is set to 1 if (( my $x = f1() ) || ( my $y = f1() )) # true, $x is set to 1, $y is undef
As in shell usage, this can be used to good effect, to perform (or skip) an action based on the outcome of previous action. (It can also be a trap for the unwary.)

In reply to Re: AND OR by graff
in thread AND OR by hasimir44

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