use strict;
use warnings;
use Data::Dumper;

while (<DATA>) {
    chomp;
    print Dumper decomp($_);
}

sub decomp {
    my @ret;
    @_ = split / /, $_[0];
    for (my $i = 0; $i < $#_; $i += 2) {
        push @ret, [$_[$i], $_[$i+1], $_[$i+2]];
    }
    return \@ret;
}

__DATA__
X -4 Y 3 Z
W 1 X -4 Y 3 Z
X 2 Y
A -4 B -4 C -4 A -4 B