use warnings;
use strict;
use feature ':5.10';
my @accel = ([-0.7437,0.1118,-0.5367],
             [-0.5471,0.0062,-0.6338],
             [-0.6437,0.1216,-0.5255],
             [-0.4437,0.3216,-0.3255],
);  # note: I changed from an array whose only element is an arrayref of arrayrefs to an array who has n arrayrefs, to be a simple 2D array

use Math::Spline;
my (@x,@y,@z,@t);
# generate x, y, and z arrays, and a t array
my $pt = 0;
for my $xyz (@accel) {
    push @t, $pt++;
    push @x, $xyz->[0];
    push @y, $xyz->[1];
    push @z, $xyz->[2];
}
# create spline calculators for x&y and x&z
my $spline_tx = eval { Math::Spline::->new(\@t, \@x) } or do { die "ty: $@" };
my $spline_ty = eval { Math::Spline::->new(\@t, \@y) } or do { die "ty: $@" };
my $spline_tz = eval { Math::Spline::->new(\@t, \@z) } or do { die "tz: $@" };

my @interp_accel = ();
my $NSTEPS = 200;
my $dt = $pt/$NSTEPS; # $NSTEPS+1 values from xmin to xmax, inclusive
for my $i (0..$NSTEPS) {
    my $t = $i * $dt;
    my $x = $spline_tx->evaluate($t);
    my $y = $spline_ty->evaluate($t);
    my $z = $spline_tz->evaluate($t);
    push @interp_accel, [$x,$y,$z]; # store for later
    printf "interpolate # %d => t=%.2f => [%s,%s,%s]\n", $i, map {$_//'<undef>'} $t, $x, $y, $z;  # debug print
}