use strict;
use warnings;
my $x= <<"__X__" x 4; # Increase multiplier for benchmarking
A data for A
B data for b
C data for c
__X__

# Method #1 - works but I don't like using $1,$2 - would rather use names
while($x=~/(^A|^B)(.+)$/mg){
  print "$1 method1 $2\n"
}

# Method #2 -

open  my $f,"<",\$x or die $!;
while(<$f>){
  my ($name,$data) = m/(^A|^B)(.+)$/ or next;
  print "$name method2  $data\n"
}
close $f;

# Method #3 (infinite loop)

#while(my ($name,$data)=$x=~/(^A|^B)(.+)$/mg){
#  print "$name method3 $data\n"
#}