$1,$2 ... has to match parens, if there is only one set of parens, $2 can NEVER be defined

'stuff' =~ /(.).../;
print "$1\n";
'stuff' =~ /(.).(.)./;
print "$1 $2\n";
'stuff' =~ /(.).(.).(.)/;
print "$1 $2 $3\n";
__END__
[download]

More in perlre,perlretut