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(tye)Re2: Unusual Closure Behaviour

by tye (Cardinal)
on Jul 13, 2001 at 03:20 UTC ( #96228=note: print w/ replies, xml ) Need Help??


in reply to Re: Unusual Closure Behaviour
in thread Unusual Closure Behaviour

Actually, that code isn't doing what you think. One way to see is to just add "use strict" to it. You'll get: Global symbol "$x" requires explicit package name

A more fun way is:

sub foo { my $x= $_[0] if ! defined $x; print "(@_):", ++$x, " "; undef $x if @_ && shift; } foo($_) for( 0,0,5,4,3,0,5,0,4,0,3 ); print $/, $x= 10, $/; foo($_) for( 0,0,5,4,3,0,5,0,4,0,3 ); print $/;
which produces:
(0):1 (0):1 (5):6 (4):5 (3):4 (0):1 (5):6 (0):1 (4):5 (0):1 (3):4 10 (0):1 (0):2 (5):3 (4):1 (3):1 (0):1 (5):2 (0):1 (4):2 (0):1 (3):2
The $x in "if !defined $x" is the global $main::x because my variables can't be used until after the end of the statement in which they were declared.

So your code is always initializing the lexical $x in your subroutine because you have never defined the global $main::x that you are checking against.

        - tye (but my friends call me "Tye")


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