The usual way to use undef on an array is like this: 

@_ = (1,2,3);
@_ = ();     # this will empty array but this will
undef @_;    # empty array and allow reallocation memory
print @_;

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Both lines shown remove all the values from @_. Underneath @_ = (); calls the C code void av_clear(AV*); whereas undef @_ calls void av_undef(AV*);

The underlying C functions differ in that in the first case memory remains allocated for the array so if you just want to empty it so you can fill it again this is the way to go. In the second case memory should be deallocated and garbage collected. If you undef an array and then go to use it again you encounter the overhead involved with setting up any new array. There is a note somewhere in the docs(can't find it) noting that using undef to empty an array is inefficient compared to setting it to ()

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

In reply to Re: using undef on a array by tachyon
in thread using undef on a array by Anarion

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