Please note in your node any substantive changes that you make (changing the code is a substantive change).

Actually once the variable name problem was fixed my earlier sample code wasn't so good. However the following revised code works as expected:

use strict;
use warnings;

my @_lines = map {"$_\n"} split /\n/, <<LINES;
ABC in the first line
but not the second
LINES

foreach my $line (@_lines) {
    my $templine = $line;
    print "$templine";
    # or  print "$line";
    if ($templine =~ /(ABC)/) {print "$1 = the line (1)\n";}
}

foreach my $_line (@_lines) {
    my $templine = $_line;
    ############   print "$templine";
    ############   # or  print "$line";
    if ($templine =~ /(ABC)/) {print "$1 = the line (2)\n";}
}
[download]

Prints:

ABC in the first line
ABC = the line (1)
but not the second
ABC = the line (2)
[download]

If this is showing your failure mode then I don't understand what the problem is. If it doesn't show your failure mode then modify my sample code until it does and post the updated code along with the "bad" output.