my $equation = '979x + 87y - 8723z = 274320';
my $vars = 'xyz'; 
my $operators = qr/[-+*\/%=]/;
my @parts = $equation =~ /([^\s$vars]+|[$vars]|$operators)/g;

##</code><code>##

perl -d
  DB<1> $equation = '979x + 87y - 8723z = 274320'

  DB<2> $vars='xyz'

  DB<3> $operators=qr/[-+*\/%=]/

  DB<4> x $equation =~ /([^\s$vars]+|[$vars]|$operators)/g
0  979
1  'x'
2  '+'
3  87
4  'y'
5  '-'
6  8723
7  'z'
8  '='
9  274320

##</code><code>##

my @parts = $equation =~ /([^xyz]+(?=[xyz])|[xyz])/g;

##</code><code>##

perl -d
DB<1> $_='979x + 87y - 8723z = 274320'
DB<2> x /([^xyz]+(?=[xyz])|[xyz])/g
0  979
1  'x'
2  ' + 87'
3  'y'
4  ' - 8723'
5  'z'