Actually they all do that, they copy the list to the "stack", its just that map introduces a scope, by the time it ends, perl has a chance to release the memory it used back to the OS -- an optimization

For a long time map/grep in scalar/void context took double the memory than equivalent for loop, so depending on perl version memory usage will differ between these two lines 

warn scalar grep {1} foo(); 
my $count = 0; $count++ for foo(); warn $count ;

[download]

wantarray is what you want to use if you want to be sure :)

In reply to Re^2: Trouble getting size of list returned from sub by Anonymous Monk
in thread Trouble getting size of list returned from sub by wanna_code_perl

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