This is behaviour is due to the fact that foreach loops alias their topic to the current value, as opposed to copying it. So when you modify $test you're changing the actual value that you're iterating over. This can be confusing, as you've noted, but it can also prove to be very handy e.g

my @strs = ('  this', '    is', '   a   ', '     list ');

s/^\s+|\s+$//g for @strs;

print "@strs\n";

__output__

this is a list
[download]

See. perlsyn for more info.
HTH

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broquaint