$ perl
use strict;
my %var;
$var{test.dot} = "a";
^D
Bareword "test" not allowed while "strict subs" in use at - line 3.
Bareword "dot" not allowed while "strict subs" in use at - line 3.
Execution of - aborted due to compilation errors.
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That's why you should use strict.

Makeshifts last the longest.