use strict;
use warnings;
use List::Util qw/reduce/;

sub _extract {
    my @names = @_;
    my @pairs;

# create all xor'd pairs
    for(my $i=0; $i<@names; $i++) {
        for (my $j=$i+1; $j<@names; $j++) {
            push @pairs, $names[$i] ^ $names[$j];
        }
    }

    no warnings 'once';
    my $or = reduce { $a | $b } @pairs;

    if ( $or =~ /\0+/ ) {
        my $index = $-[0];
        my $length = $+[0] - $-[0];
        return substr $names[0], $index, $length;
    } else { # match not successful, so return undef
        return;
    }
}

sub extract_tag {
    my @names = @_;
    my $tag;

    $tag = _extract(@names);

# try matching with reversed @names
# this finds common substrs at the end
    $tag = reverse _extract(map {scalar reverse $_} @names)
        unless defined $tag;

    return $tag;
}


my @names;
local $, = ':';
local $\ = "\n";

while (<DATA>) {
    chomp;
    print(extract_tag(@names)), @names = (), next unless /\S/;
    push @names, $_;
}
print extract_tag(@names);

__DATA__
jP|Azrael
jP|Blade
jP|Henry

Jeff.ocr
pr!me.ocr
Lokren.ocr

woRUTtan
hiRUTfango
biRUTff

salTAGo
blasTAGi
RipTAGu