You should really keep track of the index, not the value. But, if you really need to, this thread has some ways (although, most of them are golfed) to get an array index based on the value. So, for example, using jmcnamara's lovely sub:

use strict;

my @numbers = ('0.001','0.34','0.456','0.521');
my @data = ('70.1','75.3','76.5','87.4');

print $numbers[array_index('76.5', @data)];

sub array_index {
        @_{@_}=-1..@_;
        $_{$_[0]}
}
[download]

Prints 0.456

HTH

--
"I don't intend for this to take on a political tone. I'm just here for the drugs." --Nancy Reagan