Update: Added regex example.

Hello all :) I tried trimming the left side of the string. Plus incorporated the memfh example by davido. I'm curious too.

Split improves ~ 2x faster for this demonstration with Perl 5.22.x and later releases. That is the case on macOS.

use strict;
use warnings;
use Time::HiRes 'time';

my $huge_string = "aaa bbb\nccc ddd\neee fff\nggg hhh\niii jjj\nkkk ll
+l\nmmm nnn\n";

# concatenate string exponentially to 917,504 lines
$huge_string .= $huge_string for 1..17;

# memfh
{
    my $string = $huge_string;
    my $start  = time;

    open my $memfh, '<', \$string;
    my @lines = <$memfh>;
    close $memfh;

    printf "duration memfh: %0.3f seconds\n", time - $start;
    printf "%d lines\n\n", scalar(@lines);
}

# regex
{
    my $string = $huge_string;
    my $start  = time;
    my @lines;

    while ( $string =~ /([^\n]+\n)/mg ) {
        my $line = $1; # save $1 to not lose the value
        push @lines, $line;
    }

    printf "duration regex: %0.3f seconds\n", time - $start;
    printf "%d lines\n\n", scalar(@lines);
}

# split
{
    my $string = $huge_string;
    my $start  = time;
    my @lines  = split(/\n/, $string);

    printf "duration split: %0.3f seconds\n", time - $start;
    printf "%d lines\n\n", scalar(@lines);
}

# trim
{
    my $string = $huge_string;
    my $start  = time;
    my @lines;

    while ( my $line = substr($string, 0, index($string, "\n") + 1, ''
+) ) {
        push @lines, $line;
    }

    printf "duration trim : %0.3f seconds\n", time - $start;
    printf "%d lines\n\n", scalar(@lines);
}
[download]

Output - Perl 5.28.2

duration memfh: 0.384 seconds
917504 lines

duration regex: 0.387 seconds
917504 lines

duration split: 0.067 seconds
917504 lines

duration trim : 0.201 seconds
917504 lines
[download]

Another machine - Perl 5.26.1

duration memfh: 0.477 seconds
917504 lines

duration regex: 0.445 seconds
917504 lines

duration split: 0.065 seconds
917504 lines

duration trim : 0.259 seconds
917504 lines
[download]

Same machine - Perl 5.18.2

duration memfh: 0.530 seconds
917504 lines

duration regex: 0.490 seconds
917504 lines

duration split: 0.130 seconds
917504 lines

duration trim : 0.261 seconds
917504 lines
[download]

Regards, Mario