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spacebat's scratchpad

by spacebat (Beadle)
on Aug 19, 2007 at 09:36 UTC ( #633574=scratchpad: print w/replies, xml ) Need Help??

Most painful lesson learnt:

Allocation and assignment don't always happen together in a 'my' statement. Subroutine scratchpads can persist and hold on to old values.

my $var = 'value' if $condition; # this can bite

This is better written as:

my $var = $condition ? 'value' : undef; # assignment always happens
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[Eily]: oh, boolean context uses the "" overload if no bool overload has been defined
[Eily]: (I wondered if overloading bool was actually necessary)
[Corion]: Yeah, you need bool to get a true value, and the rest to return the other value ;)
[choroba]: perl -wE '{package o; use Tie::Scalar; use parent -norequire => "Tie::StdScalar" ;sub FETCH { "x" x int rand 2}} tie my $x, "o" ; say $x for 1 .. 10'
[choroba]: for complete ness

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