Assuming (as we must -- else your problem has no clean solution) that the elements in @data are unique.
Given:
my @data = ('70.1', '75.3','76.5', '87.4');
my @numbers = ('0.001','0.34','0.456','0.521');
...then just do:
my %look_up;
@look_up{@data} = @numbers;
...and then you can retrieve the values as needed. E.g.:
print $look_up{76.5}, "\n"; # prints: 0.456
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"Perl is a mess
and that's good because the
problem space is also a mess." - Larry Wall