use CGI qw(:standard);
use strict;
use utf8;

my $srce = "/some/file";
my $string1 = "some-regex";
my $last;

open my $fh, $srce or die "Could not open $scre: $!";

my @lines = grep /\Q$string1/, <$fh>;
foreach my $line (@lines) {
    my @fields = split /\s+/, $line;
    $last= $fields[3];
}
print "$last";