The variable $name in the line:

 my $outfile = "outfile[$name].txt";
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is not defined, as $name is defined within the if block, and no longer in scope (and hence no longer defined)once it leaves that block. try something like this:

#!/usr/bin/perl -w

use strict;

my $input = "transfer_to_linux.txt";
   
open (INPUT, "<$input");

while (my $line = <INPUT>){
    print "here\n";
    
    my $name;
 
    if ($line =~ /^%(.{1,100})$/){
 print "EEEEEEEEEEEEEEEEEEEEEEEEEEEE\n";
    $name = $&; 
    }
    
    my $outfile = "outfile[$name].txt";
    open (OUTFILE, "+>>$outfile");
    
    if ($line =~ /^(\d{1,6})\t(\d{3})$/){
 
 my $count = $1;
 print "COUNT: $count"; 
 my $SPSS_figures = $2; 
 print "SPSS_figures : $SPSS_figures";

 my @split = split (//, $SPSS_figures);
  
 for (my $x = 0 ; $x <= $count; $x++){
     
     print OUTFILE "$split[1]\t$split[2]\t$split[3]\n";
 
 }    
    }
}
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Note that I have not checked the rest of the code for errors, just what needed to remove the one error.

-enlil