use Data::Dumper;
my $run_cmd = "a b c >logfile.txt ";
my ($logfile) = (split />/,$run_cmd)[-1];
chomp($logfile);
my $pagal = "foo/$logfile";
my $pagal2 = "foo/logfile.txt";
print Dumper($logfile, $pagal, $pagal2);

__END__

$VAR1 = 'logfile.txt ';
$VAR2 = 'foo/logfile.txt ';
$VAR3 = 'foo/logfile.txt';