To get at the formula that results from the approximation, try this: (The normal Math::Approx methods also work on Math::Approx::Symbolic objects.)

use Math::Approx::Symbolic;

my %data = (
    (7*60+1) => 82,
    (23*60+48) => 188,
);

my $approx = Math::Approx::Symbolic->new(undef, 3, %data);

my $sym = $approx->symbolic();
print "$sym\n";

my $prettier = $sym->to_latex();
print "$prettier\n";

# Computing y-values:
print $sym->value(x => time_of_day()), "\n";

# Doing that faster:
use Math::Symbolic::Compiler;
my ($closure) = $sym->to_sub();
print $closure->(time_of_day()), "\n";

# Way faster:
use Math::Symbolic::Custom::CCompiler;
my $inlined_c = $sym->to_compiled_c();
print $inlined_c->(time_of_day()), "\n";
[download]