perl -Mstrict -W -E 'say $1 if "hello 0 and 123 goodbye" =~ /(\d)+/;'
0

##</code><code>##

$ perl -Mstrict -W -E 'say $1 if "hello and 123 goodbye" =~ /(\d)+/;'
3

##</code><code>##

$ perl -Mstrict -W -E 'say $1 if "hello and 123 goodbye" =~ /(\d+)/;'
123