Instead using x2 z2 and all as variable I tried to search them as pattern ??
Also the triple foreach make no sense to me: first a regex can be precompiled using the qr operator, second you are appliyng the regex to filename! not the content. You need a lot of practice with Perl subjects: open file, regexes (basics), loop ..

Anyway, following the basic structure mentioned by me above, and given the following folder content:

ls -l
-rw-rw-rw-   1 user     group          26 Jun 10 13:27 invalid.txt
-rw-rw-rw-   1 user     group        1049 Jun 10 13:44 reciter.pl
-rw-rw-rw-   1 user     group          36 Jun 10 13:28 valid.txt

cat invalid.txt
dfd
wdfq


qwef
z2=0.7

cat valid.txt
adf
df
x2=0.7
z2=0.7
some_t2=0.7
[download]

you must have something like (tested working code):

#!/usr/bin/perl

use strict;
use warnings;

$|++; #flush output to stdout as soon as possible
my @files = glob '*.txt';

my $pat = qr/^x2=(0.[6-9])$/;
my $pat1= qr/^z2=(0.[6-9])$/;
my $pat3= qr/^some_t2=(0.[6-9])$/;



foreach my $file (@files){
  my ($var_one, $var_two, $var_three); #your var names to be checked
  print "checking '$file'\n";
  open my $fh, '<', $file or die "...";
  while (<$fh>) {
     #use regex to put something inside  $var_one, $var_two..
     chomp $_;
     if ($_ =~ $pat)  {$var_one = $1; print "\tfound:'$_'\n"}
     if ($_ =~ $pat1) {$var_two = $1; print "\tfound:'$_'\n"}
     if ($_ =~ $pat3) {$var_three = $1; print "\tfound:'$_'\n"}
  }
  #
  #if (all vars needed are defined and pass your check){  print  "$fil
+e IS VALID\n"; system 'mv $file  /new/path'  }
  
  if (defined $var_one && defined $var_two && defined $var_three ) {

      print "FILE $file has a valid content ( x2=$var_one, z2=$var_two
+, some_t2=$var_three)\n";
      # system "mv $file x:/valid_files"
  
  }

}
[download]

and the output will be:

perl reciter.pl
checking 'invalid.txt'
        found:'z2=0.7'
checking 'valid.txt'
        found:'x2=0.7'
        found:'z2=0.7'
        found:'some_t2=0.7'
FILE valid.txt has a valid content ( x2=0.7, z2=0.7, some_t2=0.7)
[download]

HtH
L*