How can I process a multi line string one line at a time in perl with use strict in place?

Question

I\'m trying to figure out the proper PBP approved way to process a multi line string one line at a time. Many Perl coders suggest treating the multi line string as a filehandle

Answer 1

Don't initialise $ResultsHandle:

use strict;
use warnings; 

my $return = `dir`;
my $ResultsHandle;  # <-- leave undefined
my $matchLines = "";
my $resultLine = "";
open $ResultsHandle, '<', \$return;
while (defined ($resultLine = <$ResultsHandle>)) {
    if ($resultLine =~ m/joe/) {
        $matchLines = $matchLines . "\t" . $resultLine;
    }
}
close($ResultsHandle);
print "Original string: \n$return\n";
print "Found these matching lines: \n$matchLines\n";

If you leave $ResultsHandle undefined before the open(), it will be filled in with a reference to the file handle. Because you were setting it to a string, open() presumed that it was supposed to be a symbolic reference to a variable instead --- not allowed under use strict.