[me]$>perl -w regexp-test3.pl
1: ONE
Use of uninitialized value $2 in concatenation (.) or string at regexp-test2.pl line 12.
2: 
Use of uninitialized value $3 in concatenation (.) or string at regexp-test2.pl line 13.
3: 
Use of uninitialized value $4 in concatenation (.) or string at regexp-test2.pl line 14.
4: 
Use of uninitialized value $5 in concatenation (.) or string at regexp-test2.pl line 15.
5: