chromatic has found the cause of your problem, but just to show another way to initialize the %vals hash, here is a way that doesn't split but instead, captures the key/value pairs.

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my %vals = map /(\S+)\s*=\s*(\d+)/g, <DATA>;
print Dumper \%vals;

__DATA__
x1=2; x2=3; x3=4;
y1=3; y2=5; y3=7;
z1=4; z2=7; z3=10;
[download]

The output of Data::Dumper is

C:\Old_Data\perlp>perl t5.pl
$VAR1 = {
          'y1' => '3',
          'z1' => '4',
          'x2' => '3',
          'z2' => '7',
          'x1' => '2',
          'x3' => '4',
          'z3' => '10',
          'y2' => '5',
          'y3' => '7'
        };
[download]

Hope this is of some use, Chris