Because you're declaring a variable in a loop and it falls out of scope outside of the loop e.g 
perl -we "my $a = q[foo] for 1; print $a"
Use of uninitialized value in print at -e line 1.

[download]
It's statement modifier abuse essentially.
HTH

_________
broquaint

In reply to Re: Mysterious append failure. by broquaint
in thread Mysterious append failure. by BrowserUk

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