ok, -w and use warnings don't make sense.
Yes, you are correct with the equal - output and the numbers.
change

 
my @file = ('0.13','0.14','0.14');
my $diff = 0;
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to

 
my @file = (0.14,0.14);
my $diff = -1;
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and here you got your output

Difference between 0.14 and 0.14 is 0
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