use strict;
use warnings;

my ($ikegamiRe1) = map qr/$_/, join '|', map "(?<=$_{3})$_+", map quotemeta,
    1 .. 9;

##</code><code>##

Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.
Use of uninitialized value in concatenation (.) or string at noname.pl line 4.

##</code><code>##

use strict;
#use warnings;

my $str = join '|', map "(?<=${_}{3})$_+", 1 .. 2;
print $str, "\n";
$str = join '|', map "(?<=$_{3})$_+", 1 .. 2;
print $str;

##</code><code>##

(?<=1{3})1+|(?<=2{3})2+
(?<=)1+|(?<=)2+