my $reject_rx = qr{
    total [ ] rows [ ] rejected: [ ] (\d+)
|
    (\d+) [ ] rows [ ] rejected
}x;

if ( $line =~ /$reject_rx/ ) {
    my $count = defined $1? $1 : $2;
    print $count, "\n";
}

##</code><code>##

use 5.010_00

my $reject_rx = qr{
(?|           # either match will be in $1
    total [ ] rows [ ] rejected: (\d+)
|
    (\d+) [ ] rows [ ] rejected
)
}x;


if ( my ($count) = $line =~ /$reject_rx/ ) {
    say $count;
}