OK, except I don't see 2 hits on the second line, I see 3:

SUUTINKÄRKI SPRAY TP 9501 E-SS;SUUTIN  VALME HOL0125624 TP 9501    E-S
+S
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TP, 9501, and E-SS.

This is my version 2:

#!/usr/bin/perl 
use strict;
use warnings;  

my $readfile  = 'blah.csv';
my $writefile = 'bleh.csv';

open my $fh,  "<", $readfile  or die "Unable to open $readfile: $!";
open my $wfh, ">", $writefile or die "Unable to open $writefile: $!";

foreach (<$fh>) {
    
    $_ = uc $_;
    
    chomp;
    
    my ($col1, $col2) = split /;/;
    my @col1_words = split /\s+/, $col1;
    my @col2_words = split /\s+/, $col2;
    
    my $found = 0;
    my $pattern = join ('|', @col1_words);
    
    for my $col2_word (@col2_words) {        
        $found++ if $col2_word =~ /$pattern/;
    }
    
    print $wfh "$_;".@col1_words.";$found\n";
    
}

close ($fh);
close ($wfh);
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