perl -le '$s="a1, a3 - a5\na11"; while ($i<10) { $i++; $s=~?a(\d+)?g; print $1; }'

##</code><code>##

perl -le '$s="a1, a3 - a5\na11"; while ($i<10) { $i++; $s=~/a(\d+)/g; print $1; }'

##</code><code>##

perl -le '$s="a1, a3 - a5\na11"; $s=~?a(\d+)?g; print $1; $s=~?a(\d+)?g; print $1; $s=~?a(\d+)?g; print $1; $s=~?a(\d+)?g; print $1;'